'I LINGUAL MANUAL
SOLUTION PREVENTION
Waste
Minimization
for the Metal
Developed by
U.S^ EPA/SEDESOL
Pollution Prevention
Workgroup
May 1993
-------
SECTION I
Introduction
Sfc^
Jf'Kfe"". a
-------
CASE STUDIES FOR THE METAL ,
FINISHING INDUSTRY
This appendix provides four case studies of waste minimization efforts in the metal
finishing industry. The case studies provide examples that coyer the range of
pollution prevention options existing in this industry. Recognizing that waste
disposal costs differ between Mexico and the United States (from where these
case studies originate), the case studies provide examples of potential savings.
Moreover, health and other benefits often result when a pollution prevention
.program is implemented. . ' " . ,
The four case studies in this, appendix were derived from diverse spurces, thus the
material contained in each case study may differ slightly from the other three
studies presented in this appendix. Numerous case studies, other than those
presented in this appendix, have been written in the United States. The reference
list in the back of this manual lists sources for additional case studies.
CASE STUDY NO. 1:
MANUFACTURER OF COMPONENTS FOR AUTOMOBILE
AIR CONDITIONERS1
INTRODUCTION
Case Study No. 1 presents waste minimization efforts at a plant that manufactures
three distinct product components for automobile air conditioners: (1) charged air
coolers, (2) round tube plate fin (RTPF) condensers, and (3) air conditioning tubes.
WASTE GENERATION ACTIVITIES
Charged Air Coolers
When manufacturing charged air coolers, sand^cast aluminum tanks are cleaned
in an aqueous alkaline bath at 160 degrees Fahrenheit (°F), rinsed in successive
stages, air dried, and inspected. Air and turbulator fins! headers, and side sheets
are fabricated, hand-assembled into air "coolers, brazed, and painted. The wastes
generated by these processes include: . ,
Lubricating oil, generated (1) wheh.coil stock is made into air fins, turbulator
fins, headers, and side sheets and (2) when extruded aluminum tubes are
cut to length and debarred '-N:
'" Scrap metal, generated when headers and side sheets are made from-
; aluminum coil stock - ; '
Spent solvent (trichloroethane, perchldrethytene), generated during
degreasing operations - . ..;','.
Paint booth waste containing sblvent^and paint, generated during paint gun
cleaning; water, generated when water rjuns off the paint booth's water
curtain; waste paint solids; and overspray\
1 Taken from, "Pollution Prevention Case Stuates.Compendium,' U.S. Environmental Protection Agency, Office of
Research and Development, Washington, D.C. 20460, EPA/600/R-046, April 1992
CASE STUDIES. ' . . .
-------
RTPF Condensers
When manufacturing RTPF condensers, steel headers, aluminum hairpins, and
aluminum'coil stock (for fins) are fashioned into parts, degreased using,
perchlorethylene, dried, assembled into the condenser body, brazed, flushed with
hot water, leak tested, oven dried, and dip painted. These manufacturing
operations generate wastes similar to those generated when charged air coolers
are manufactured.
Air Conditioning Tubes
When manufacturing air conditioning tubes, aluminum coil tubing is cut to length,
formed, and straightened. About 39 percent of the product is degreased using
trichloroethane. The other 61 percent is welded, pierced, and welded again before
being degreased, dried, and leak tested. Cutting oils and solvent wastes are
generated by these processes.
WASTE MANAGEMENT ACTIVITIES
This plant generates several different types of waste annually. Approximately 40
barrels of spent oil are disposed of off site. Twenty-five barrels of still bottoms (one
third of which is trichtoroethene. the remainder of which is perchlorethene) are
disposed of off site. Approximately 1.4 million gallons of process wastewater is ,
treated at the facility and emptied into the sewer. Approximately 250,000 pounds
of aluminum and steel scrap is sold as refuse. Twenty barrels of paint sludge are
disposed of as hazardous waste.
The plant presently has a solvent distillation unit used to recover spent.solventand
a secondary still used to recover solvent from the bottom of the first still. The plant
has virtually eliminated sludge from its wastewater treatment system. The plant
sells scrap aluminum and steel generated on site for $146,500 per year.
WA STE MINIMIZATION OPPORTUNITIES
By replacing the chlorinated hydrocarbon solvents wtth'degreasers that can be_
directly discharged to sewers, waste disposal costs would be reduced by $6,007
per year and raw material cost savings would amount to $62,640 per year. The
payback period for the $20.700 implementation costs would be about 4 months
Note that of the 11,000 plus gallons of solvent used each year, 92 to 98 percent is
lost to evaporation.
By not feeding water to idle rinse tanks arid by converting thesetanks to a _ _
cbunterftow rinse system, $33,235 would be saved each year. The payback penod
£*»$a*a^Sptementattoncost would be about 1 month. By converting present
painting operations to electrostatic powder coating, waste solvents and other
wasteS irSuding water, paint solids, used plastic liners, and spray tmtti coabng.
would bVreduced or eliminated. Each year, waste d.sposal costss wouldI be
reduced $5 869 and raw material cost savings would amount to $22,885. Tne
paybackperiod forthe $100,640 implementation cost would be 3.5 years.
By fabricating lightweight plastic tops and using them to cove r the ^greasing units
when not in use, solvent evaporation would reduce raw material costs by' $26^75
per year. The payback period for the $3,600 implementation cost would be about 1
month. ,
WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
CASE STUDY NO. 2:
METAL RECOVERY DRAGOUT REDUCTION2
Case Study No. 2 presents waste minimization efforts at an electroplating facility;
These efforts were undertaken as part of the Minnesota Waste Management
Board's MnTAP program, which is supported by a grant to the School of Public
Health, Division of Environmental and Occupational Health, at the University of
Minnesota.!
INTRODUCTION
New Dimension Plating is an electroplating facility that employs about 40 people in
Hutchinson, Minnesota. While the plant plates a variety of metals, including gold
and brass, most of the plating activities at the plant involve applying chromium to
, objects that have been previously coated with copper and nickel. Hazardous
waste is generated by plating tank dragout. This waste contained a significant
amount of chromium and smaller quantities of nickel, chlorine, and copper.
WASTE GENERATION ACTIVITIES
The plant's original electroplating system used a stagnant rinse tank and three
countercurrent rinses to remove excess chromium solution from newly plated
parts. The initial stagnant rinse tank received a large portion of the chromium. The
contents of this rinse water were then gradually returned to the plating tank to
replace evaporated solution. Wastewater frorri the first, most cpncentrated, rinse in
the countercurrent rinse series drained to the plant's pretreatment system where
chromium was removed during sludge production (see Rgurel).
WASTE MTNTMT7ATION OPPORTUNITIES
New Dimension Plating redesigned its electroplating system and hazardous waste
pretreatment system to meet the following goals:
Maintain high quality plating
Reduce the amount of chromium dragged out of the plating bath
Reuse chromiumlin the plating bath -; ^
Reduce sludge'production
Reduce the use of treatment chemicals
To reduce the amount of chromium dragout, New Dimension Plating decided to
install a drip bar in a spray rinse tank. New Dimension built the spray rinse tank
. and drip bars in the original system's stagnant rinse tank. The new system allows
the company to reduce dragout by providing longer drip time, thus avoiding the
possibility of staining. By adjusting the size of the nozzles and the length of
spraying time, the amount of rinse water solution can also be controlled. By
increasing evaporation in the chromium tank, all of this solution can be returned to
the plating tank on a daily basis, thereby reducing the amount of dragout that
continues through the rinse system (see Figure 2).
2 Taken Irom, 'MnTAP,' Minnesota Technical Assistance Program, date unknown
CASE STUDIES ''..' ', ; '"-
-------
Figure 1 - Original System
Processing and
Undercoating
Plating Bath
Wastewater
from rinse
Chromium
Plating Bath
Co
untercurrent
Rinses
^
i Return to
i plating bath
; to replace
: evaporation
Wastewater from most
concentrated rinse
I
Treatment with
metabisulphate
i
Original Pretreatment Plant
(Sodium Hydroxide + Fitter Press + Sludge Drier)
New Dimension Plating was meeting current regulations for wastewater discharge, but the
operation of the system was very expensive. The company wanted to reduce chromium waste and
cut treatment chemical costs, but maintain a high level of plating quality.
The approximate cost of the new equipment is as follows:
Evaporators
Pumps
Spray nozzles, racks
PPS2 Purifier
Installation
Total Cost
$1,000
$1,000
$50
$350
$500
$2,900
The operating cost of the new system is minimal, with no added costs for utilities
or supplies. Additional labor consists of approximately 1 hour every 2 weeks.
The first of the three original countercurrent rinse tanks was converted to a
stagnant rinse tank, and the last two were combined into one large continuous
'rinsetank.
New Dimension built evaporators to reduce the volume of water in the plaiting tank.
The stagnant rinse tank was built to allow all of the spray rinse solution and some
of the stagnant rinse water to be returned to the tank each day.
An electropurification module was installed directly into the plating bath to remove
contaminants from the returned dragout solution without interrupting the plating
process. New Dimension Plating chose the Model PPS2 porous pot chrome
solution purifier, manufactured by Hard Chrome Plating Consultants of Cleveland,
Ohio. The company is completely satisfied with how this unit functions and felt that
other manufacturers could obtain similar results with this type of unit.
WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
Figure 2 - New System
. . r . . --''-'''-.'" . ' '
--'' ' " : ' - ' ' '-".
/* N
Processing and
Undercoating
Plating Bath
V J
Wastewatei
from rinses
r*
V
r \
1 Evaporator I
1 J
r \
^ Chromium i
.^" Plating Bath ~
> '<
r Electro- A
L purification I
^ Module , J
, - -'. ' '
Spray c. * '
fc, Rinse ^ Stagnant . chromium
w Tank with ~"^ Tank ^ Plating Bath
Qa/*l^e ^^ ' '
. i . - . .
_._ _. , , . _ i
Return to \ Partial return to ...
plating bath :' i plating bath to
toreplaca j [ replace Wastewater from most
avaporaaoh i' evaporation concentrated rinse
Treatment with
metabisulphate
Original Pretraatment Plant '
(Soctum Hydroxide + FiK9rPi9a3 + Sludg9Driot)
: "' ': " . ' J
As a result of the new system, the amount of chromium dragout fed into the stagnant rinse tank
was reduced from 7 pounds to 1 pound per day.
RESULTS AND DISCUSSION
Change:
installation of the spray rinse and drip
bar in the existing stagnant rinse tank.
Conversation of counter-current rinses
into one stagnant rinse and one large
continuous rinses'^ '
Installation of the electro-purification unit
(the Mode IPPS porous potchrome
solution purifier) In the chromium plating
tank.
Results;
This initial rinse following the
chromium plating reduces dragout in
the system because all of the rinse
water is returned to the plating tank.
The new rinse system reduces water
flow from 1.2 gallons per minute (gpm)
to 1.0 gpm. The large rinse tank
makes rinsing of the large parts more
efficient.
The unit allows reuse of the dragged
out chromium by removing
contaminants from the rinse water
retume
CASE STUDIES
-------
By using a spray rinse system with a drip bar following the chromium plating .bath,
New Dimension Plating has reduced dragout from 7 pounds to 1 pound daily.
When combined with in-tank electropurification of metal contaminants, this
reduction reduced sludge production and saved an estimated $7,000 associated
with the purchase of chromium and treatment chemicals. New Dimension has
been quite satisfied with the results of the new system.
CASE STUDY NO. 3: WASTE MINIMIZATION ASSESSMENT
FOR A MANUFACTURER OF SHEET METAL CABINETS AND
PRECISION METAL FARTS3
INTRODUCTION
Case Study No 3 presents waste minimization efforts at a plant that manufactures
sheet metal cabinets and precision metal parts. Approximately 1.15 million parts
. are produced annually by 140 employees who operate the plant 2,210 hours per
year To make the cabinets, sheet metal is cut to size, bent, welded, and polished.
The surface of the metal parts is then treated and painted. The machined parts are
produced from bar stock that is cut, drilled, milled, and ground as needed. Most of
the waste at the facility is generated by the chromate conversion and iron
phosphate coating processes. These processes are used to prepare the parts for
painting. .
WASTE GENFtt ATTON ACTIVITIES
When making the metal cabinets, sheets of aluminum and steel are cut to the
proper size and shape, and holes are punched into the metal. The metal is then
bent and welded together as needed. Rough edges and surfaces are polished
using power senders and buffers. Scrap metal is shipped to a scrap metal dealer
for recycling. Spent cutting fluid and waste hydraulic oil are combined and shipped
off site for recycling or incineration.
Before painting, the surface of the metal parts is treated to improve paint bonding
and provide corrosion protection. Aluminum parts receive a chromate conversion
coating, and steel parts receive an iron phosphate coating.
During treatment, aluminum parts are dipped in a caustic cleaning solution and
rinsed in a continuous-flow tap-water rinse. The parts-are then dipped in a third
tank containing a desmut solution and rinsed again in another continuous-flow tap-
water rinse. Next, the parts are placed in a chromic acid-based chromate
conversion solution, rinsed in another continuous-flow tap-water rinse, and finally
placed in a tank containing a heated dead-rinse of tap water. The caustic cleaner,
desmut, and first rinse tanks are dumped monthly; the chromic acid tank is
dumped every 3 to 4 years; and the remaining solutions are dumped every 5
months. In addition, sludge accumulates in the caustic cleaner tank, which is
cleaned monthly.
When coating steel parts with iron phosphate, the parts are dipped in ^caustic
cleaning tank and then rinsed with a continuous-flow tap-water nnse. The parts; are
then dipped in a tank that contains an iron phosphating solution and subjected to
. another continuous-flow tap-water rinse. The parts are finally dipped in a
deoxidizing solution. All of these baths are dumped and replenished on a monthly
' basis. Combined wastewaters from the iron phosphate and chromate conversion
> Taken Iron, -Znvinnmentol Research Brief.' U.S. Environmental Protection Agency. Research and Developrrsnt. RisK
ReducttonEngineering Laboratocy. Cincinnati. OH 45268. EPA/600/S-92/019. May 1992
. WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
lines drain to an overflow tank. These wastewaters are then drained to the sewer
as industrial wastewater. Typically, the wastewaters are not pretreated prior to
discharge because the wastewater meets discharge limits set by the publicly
owned treatment works (POTW). Sludge accumulates in the caustic cleaner and
iron phosphate tanks and is disposed of monthly.
Solvent-based paint is applied to metal parts in dry paint booths. Waste paint,
generated when the paint mixture becomes too thick, is shipped to a hazardous
waste treatment, storage, or disposal facility (TSDF). Spent paint thinner is also
shipped off site. Painted parts are dried and cured in ovens. The plant uses
powder-based paint coatings on a few parts. The type of paint used is dictated by
the customer's requirements..
When producing machined parts, bar stock is cut, drilled, milled, and ground as
needed. Finished parts are assembled (if required) and shipped to customers.
Mejal scrap is shipped to a scrap metal dealer for recycling. Spent cutting fluid and
waste hydraulic oil are combined with similar wastes and shipped off site for
recycling or incineration.
WASTE MANAGEMENT ACTIVITIES
This plant takes the following steps to manage its wastes:
-,/ / - _
Scrap metal is segregated on site and sold to a recycler .
To contain spills, all reagent tanks in the phosphating and chromating lines
are located in a large pit with a central drain. -
Drain boards are used between surface treatment tanks to reduce dragout.
Reagent solutions in the surface treatment lines are agitated with air to
increase their effectiveness." . - ,
Dry paint booths are used to paint metal parts, thus avoiding the aqueous
paint-laden wastes that are generated by wet paint booths.
A small powder coating unit is used to paint some products, thus avoiding
the use of solvent-based paints.
Tank dumps are coordinated to achieve neutralization so that the effluents
discharged to the POTW meet wastewater requirements.
WASTE \nNIMIZATTONOProRTUNITIES
Table 1 shows the opportunities for waste minimization at the facHity. The present
practices, recommended actions, and waste reductions and their associated
savings are aiso given in Table 1. The quantities of hazardous waste currently
generated by the plant and possible waste reduction depend on the plant's
production level. Allvalues should be considered in this context.
It should be noted that, in most cases, the economic savings associated with
waste minimization opportunities result from the need for less raw material and
from reduced present and future costs associated with the treatment and disposal
of hazardous waste. Other savings that are not^quantifiable include future costs
related to changing emissions standards as well as costs associated with liability
and employee health. It should also be noted that the savings given for each
opportunity reflect the savings achievable when independently implementing each
waste minimization opportunity; they do not reflect the duplicate savings that
would result when the opportunities are implemented as a package.
CASE STUDIES
-------
In addition to the opportunities recommended and analyzed in Table 1, several
additional measures are presented below. These measures were not analyzed
completely because of insufficient data, implementation difficulty, or a projected
lengthy, payback. Since one or more of these approaches to waste reduction may
become more attractive over time, they were brought to the plant's attention for
future consideration.
Install filtration units for the iron phosphating and caustic cleaner solutions to
increase solution life.
Use deionized water to make-up and maintain the caustic cleaner and iron
, phosphating solutions, thereby reducing sludge formation.
Substitute nonchromate conversion coating for conversion coating currently
used on aluminum parts.
Increase drainage times over the tanks in the iron phosphating and chromate
conversion lines in order to reduce dragout.
Segregate and recycle waste oil from the spent cutting fluid.
Implement a preventive maintenance program in the machine shop to reduce
the quantities of spent cutting fluid and waste oil.
CASE STUDY NO. 4: WASTE MINIMIZATION ASSESSMENT
FOR A MANUFACTURER OF METAL-PLATED DISPLAY
RACKS4
INTRODUCTION
Case Study No. 4 discusses a plant that manufactures metal-plated display racks.
The plant's 200 employees process approximately 10 million pounds of metal
annually and operate the plant 4,160 hours per year. During this process, steel
wire, tubing, and sheets undergo machining operations, and the resulting parts are
nickel and brass-plated, nickel-plated, zinc-plated, nickel and chrome-plated, or
painted. The various finished parts are then assembled into display racks. The
majority of waste at the facility is generated by the plating lines.
WASTE GENERATION ACTIVITIES
The raw materials used to make the display racks include steel wire, tubing; and
sheets; nickel, zinc, and brass plating anodes; cleaning agents and plating solution
chemicals; and powder and liquid paints. Approximately 40 percent of the finished
products are nickel and brass-plated, 26 percent are nickel-plated, 24 percent are
zinc-plated, and 10 percent are nickel and chrome-plated.
The steel wire, tubing, and sheets undergo stamping, bending, forming, shaping,
welding, and riveting. The partsto be plated are then sent through one of the three
following plating lines. Other parts are sent to the paint line, which is also
descrfced below. -~v
'" \
4Taken from. 'EnvtmnmrntalRosMKh B/teC U.S. Environmental Protection Agertey, Office of Research and
Development. RWc Reduction Engineering Ltboratoiy, Cincinnati. OH, EPA/600/S-92/021. May 1991
8 . WASTE MINIMIZATION IN THE METAL FINISHING,INDUSTRY
-------
/ Table! A-
Waste Minimization Recommendations
Solvent-based paints are used to
coat the majority of this plant's
products. Waste paint, paint
sludge, and spent thinner are
disposed of offsite.
A solvent recovery unit in the
plant currently is not operational
because of oil and water leaks.
Cutting fluid is used until it
becomes malodorous or until its
viscosity and lubricity are
unacceptable. Average fluid
lifetime is about 3 months.
Replace solvent-based painting
'with powder-based painting for a
portion of the plants products.
Cost savings will result from
reduced disposal costs and
reduced raw material costs.
Installation of a batch spray booth
for powder coating will be
required.
Replace solvent-based painting
with water-based painting for a '
portion of the plant's products (a
separate portion from previous \
WMO). Cost savings will result
from reduced disposal costs and
reduced raw materials costs. This
change requires the purchase of
new paint application equipment
and may require increased curing
times.
Waste reduction = 72 gallons per
year (gal/yr) (waste paint and
paint sludge) + 66 gal/yr (spent
thinner); Waste management
cost savings = $740 per year;
Net raw material cost savings =
$14,230 per year; Total cost
savings = $14,970 per year;
implementation cost = $20,600;
Simple payback = 1.4 years
Waste reduction = 72 gal/yr
(waste paint and paint sludge) +
66 gal/yr (spent thinner); Waste
management cost savings =
$740 per year; Net raw material
cost savings = $10,930 per year;
Total cost savings « $11,670 per
year; Implementation cost =
$2,500; Simple payback = 0.2
year
Overhaul the solvent recovery unit
to permit reuse of spent paint
thinner. Cost savings will result
from reduced disposal costs and
reduced purchases of thinner.
Institute a program to recycle the
cutting fluid onsite. Fluid should
be filtered periodically to remove
metal chips and particulate matter,
thereby extending the life of the
cutting fluid. In addition, the spent
cutting fluid can be treated wffli
acid to reduce (he volume of
wastes that must be shipped
offsite. The addition of acid will
cause a phase separation;: the
aqueous phase can be neutralized
arid sewered and the organic
phase should be disposed of
offsite.
Rinse water rates set by operators Install a flow reducer and flow
exceed flow rates required by the meter In the.water supply line
rinses in the chromata conversion
and phosphating lines, £ '
upstream of the rinses in the
cnromato conversion and iron
phosphating lines, thus reducing
the quantity of water purchased
and sewered
Waste reduction - 660 gal/yr;
Waste managementoost-
savings « $3,890 per year;
Net raw material cost sayings »
$1,780 per year; Operating cost
of recovery unit = $430 per year;
Net cost savings = $5,240 per
yean Implementation cost =
$2,500; Simple payback = 2.1
years
Waste reduction = 425 gal/yr;
Waste management cost
savings » $2,920 per year;
Net raw material cost savings =
$570 per year; Operating cost'of
filtration unit = $370
per year; Total cost savings =
$3,120 per year; Implementation
cost * $7,050; Simple payback a
2.3 years
Waste reduction - 331',500 gal/
yn Waste management cost
savings'« $1,000 per year; Net
raw material cost savings - $510
per year; Total cost savings »
$610 per year; Implementation
cost - $100; Simple payback *
0.2 year ' . '
CASE STUDIES
-------
BARREL PLATING LINE *
Small fabricated parts are cleaned prior to plating to remove residual oils and
qrease by using either a vibrating cleaning unit or a rotating abrasive tub. The
vibrating tub cleans parts by vibrating them in a chemical solution. Spent cleaning
solution and rinse water are sent to the plant's wastewater treatment facility. In the
rotating abrasive tub, the parts and abrasive pellets are placed in small rotating
tubes. Spent abrasive pellets are disposed of in a landfill.
The cleaned parts are placed in hollow barrels that are attached to an overhead
conveyor system. The barrels, which have holes along the length of their surfaces, -
are then slowly rotated while submerged for a specified amount of time in the
plating line's various tanks.
Each batch of parts to be plated undergoes specific steps in the line. All of the
pieces pass through 'most of the same preparatory stages, while later stages in the
line are reserved for one type of plated part only. Plated parts are then sent to
other areas of the plant for assembly. Spent solutions in all the tanks, except the
plating baths, are dumped to the plant's wastewater treatment facility.
ZINC PLATING LINE
Larqer-size metal pieces are manually hung on racks attached to an overhead
conveyor system that is used to dip parts in the 22 tanks that make up this line.
Plated parts are transferred to the assembly areas of the plant. AH spent tank
solutions are piped to the plant's wastewater treatment facility.
FRAME PLATING LINE
The frame plating line is used to plate nickel, nickel and chrome, and nickel and
brass onto large display rack frames. Parts are hung on racks as in the zinc-
plating line. Some of the tanks in this line are bypassed, depending on which type
of plating is required. Finished parts are transferred to the assembly areas of the
plant. Spent tank solutions are sent to the plant's wastewater treatment facility.
PAINTLINE
Miscellaneous metal pieces that do not require plating are sent to the three-stage
washer and paint areas. The parts are hung on a small conveyer system that
transports the parts through an enclosed washer line containing three different
solution-filled tanks. Spent solutions are dumped directly to the municipal sewer,
After cleaning and drying, parts are painted using electrostatic powder coating or
liquid dip painting. Overspray powder is collected and reused. Dragout from the
dip painting process is collected on cardboard or plastic sheets that are disposed
. of in a landfill. After drying, the painted parts are transferred to the assembly areas
of the plant.
WASTE MANAGEMENT ACTIVITIES
" ' The plant operates an electrostatic powder paint system to reduce the
amount of paint wastes it generates.
The plant uses water-based, nonhazardous liquid paints.
Filtering systems recover zinc and nickel from spent plating solutions.
...y7 }WAST£.MttffMEAtrON IN THE METAL FINISHING INDUSTRY
"1C" "
-------
Cyanide-laden brass plating water is stored in a holding tank and used as
rinse water by several of the plating line stages, ,
- " "'" ' " "?'-' " ' ' ....""
All wastewater is treated on site before release to the municipal sewer.
A natural gas-fired dryer is used to reduce the volume of sludge resulting
from the filter press operation. ,, :
WASTE MINIMIZATION OPPORTUNITIES
Table 2 shows the opportunities for waste minimization at the plant. The type of
waste, the minimization opportunity, the possible waste reduction, and its
associated savings and implementation cost, including its payback time, are
presented,^ the table. The quantities of waste currently generated by the plant
and possible waste reduction depend on the plant's production level. All values
should be considered in this context.
It should be noted that the economic savings associated with each waste
minimization opportunity, in most cases, results from the need for less raw
material and from the reduced present and future costs associated with treatment
and disposal. Other savings that are not quantifiable include a wide variety of _ *
possible future costs related to changing emissions standards as well as the costs
associated with liability and employee health. It should also be noted that the
savings given for each opportunity reflect the savings achievable when
independantly implementing each waste minimization opportunity; they do not .
reflect duplication of savings that would result when the opportunities are
implemented as a package. '
Table2
Waste Minimization Recommendations
(Sheetlof2)
Present Practice
Contaminated plating, wash, and
rinse water from the barrel, zinc,
and frame plating lines and
contaminated wash and rinse
water from the paint line are
treated on site and sewered.
As the nickel plating baths In the
barrel and frame plating lines
becoms contaminated, they are
emptied'into dedicated filtering- ,
units used to recover a larger
portion of the particulata nickel in
the solutions. The filtering units
are periodically backflushed with
a weak acid solution., The acid
solution, which contains
contaminants, is sent to the
plant's wastewater treatment
facility. Currently, a significant
amount of nickel is discharged in
the'wastewater sludge which, as
a result, is classified as a
hazardous waste.
Proposed Action
Install a piping system to recycle
treated wastewater within the
plant to reduce purchases of
water. If necessary, improve the
current methods of wastewatar
filtering to provide sufficiently
clean water.
Modify the ptating lines in
question to incorporate the
utilization of a zero discharge
recovery (ZDR) system. It is
recommended that the system
use reverse osmosis technology
to recover plating bath solutions
at plant-specific concentration
levels. The system will operate in
a closed-loop manner. There-
fore, the amount of nickel
discharged to the wastewater
treatment facility will be reduced.
A portion of the chemicals\
required by the baths and by the
water treatment facility will no
longer be needed. Approximately
the same amount of sludge will .
be generated, but it will be'--,
classified as nonhaz:
Waste Reduction and
Associated Savings
Estimated waste reduction =
3,114,290 gallons per year (gal/
yr); Net raw material cost savings
= $11,120 per year; Operation
cost = $3,840 per year; Total cost
savings = $7,280 per year;
Implementation cost = $56,380
per yean Simple payback '» 7:8
years
Estimated, waste reduction =
none; Waste disposal cost
savings ~ $24,460 per year; Net
raw material cost savings »
$6,250 per year; Operating cost =
$8,000 per yean Total cost
savings = $22,710 per year;
Implementation cost = $70,000;
Simple payback = 3.1 years
CASESTUD/ES
11
~-T
-------
Table 2
Waste Minimization Recommendations
(Sheet 2 of 2)
Present Practice
Add wash tanks, which are used
in each of the plating lines (or
cleaning of metal parts, are sent
to the wastewater treatment
facility as they become contami-
nated.
Rinsing in the plating lines is
accomplished by dipping parts in
rinse tanks. As a result, consider-
able dragout and contamination
occur. Spent water from the
rinsing tanks is dumped to the
onsite wastewater treatment
facility, treated, and released to
the municipal sewer.
Dragout in the three plating lines-
current accounts for an estimated
10 percent loss in chemical
solutions.
Various tanks in the plating and -
paint lines are steam heated.
Condensate is not returned to the
boiler because of concerns about
possible contamination. It is sent
to the waste treatment facility.
Proposed Action
Recover and reuse the spent salt/
acid solution from the contami-
nated wash tanks. It is estimated
that 70 percent of the acid salt
can be recovered using an
evaporator and reused. Implemen-
tation of this recommendation will
lead to a reduction in the amount
of acid and salt purchases.
Wherever possible, modify the .
zinc and frame plating lines to use
spray rinsing techniques instead
of dipping objects in tanks.
Install rinse devices above each
plating and wash tank in the zinc
and frame plating lines to spray
water on parts as they are '
removed from tanks. As a result,
plating solutions will be returned
to their tanks before dragout
occurs.
Install individual heat exchangers
to serve each heated wash tank
and plating bath. The proposed
units should transfer heat from
the main steam line to smaller
lines feeding each tank. There-
fore, the steam will not come in
contact with any process fluids
and can be returned to the boiler.
Waste Reduction and
Associated Savings
Estimated waste reduction = 42
gal/yr (waste solids) + 30,860
gal/yr water; Waste mansigement
cost savings = $390 per year;
Net raw material cost savings =
$7,700 per year; Total cost
savings = $8,090 per year;
Implementation cost = $29,440;
Simple payback = 3.6 years
Estimated waste reduction =
617,760 gal/yr; Net raw material
cost savings = $2,200 per year;
Implementation cost = $16,900;
Simple payback » 7.7 years
Estimate waste reduction =
none; Net raw material cost
savings = $2,800 per year;
Implementation cost = $17,940;
Simple payback = 6.4 years
Estimated waste reduction =
262,000 gal/yr; Net raw material
cost savings » $940 per year;
Energy cost savings - $870 per
year; Boiler feedwater chemical
cost savings = $3,500 per year;
Total cost savings » $5,310 per
year; Implementation cost =
$33,700; Simple payback = 6.a
years
12
|jONy» THE^ETVU. FRESHING INDUSTRY
*. ***& "^
-------
ATTACHMENT A
Information on
Accessing Pollution
Prevention Information
Clearinghouses
-------
ATTACHMENT B
Survey
-------
MAILING-LIST FOR FUTURE PUBLICATIONS
Name: ' - - '. - . X3raani"zation;
Positipn: . .' ' " ; Address:
.Phone: . _i ; ' ...- ;~ :
Fax: ; 1 - ' ._
SURVEY:
DID YOU FIND THIS MANUAL USEFUL?
» Please help us by answering the following questions:
A.-.1. PROFILE OF YOUR ORGANIZATION
Trade association- '' ' / / Business 7 / Governmental-office
/ / Other . ' ' - ''.-' ' ' -' -.- -: -' ' ' '-''/..
/ - - . , - . - - - ' ,
What product or service does your business/organization provide? " ' '
How old is your business/organization? 1_ years
- . . ' . - .- ','' ^ -
How many employees.work in your business/organization?
B.- ': TRAINING . _ . . ^ . .
'J.S. EPA and SEDESOL plan to add sections to this manual to support other industries in the border-
area. Which industries should be addressed next? . . .
7 / Agricultural'.Chemical-s / / Wood Finishing /../' Other '.
' ' ' " ' ' ' '
*?hat type of training would you attend? V ,
r " , , - ' . , '
/ / Technical workshops / / deneral training / / None .'./"/ Other
EPA and SEDESOL are considering holding training sessions on "pollution prevention.
information would be -useful to you in '
- .
-------
- 2 -
C. USEFULNESS OF MANUAL
Did you find the format of this manual useful? ' / / Yas / /Ho.
Did you find its content useful? / / Yes / / No
How would you improve it? _
What other information should be included?
Who else should receive this manual?
Name:
Address: __ _
D. ADDITIONAL COMMENTS
Please provide any additional comments on this manual and its usefulness,
Please fold on the dotted line and mail. If you have kny questions, regarding this publication or would like additional
information, you may contact U.S. EPA (415) 744-1500, or SEDESOL 525-553-6421.
Place
Stamp
Here
HILARY LAUER
.POLLUTION PREVENTION COORDINATOR
US EPA (H-l-B)
75 HAWTHORNE ST
SAN FRANCISCO CA 94105-3901
(Place tape here)
-------
-FOLLUTIQN PREVENTION
"*" »? f VV
APPENDIX A
Referenqing Additional
Information
-------
N. .
-------
APPENDIX A: ADDITIONAL INFORMATION
The following are additional documents on pollution prevention that you may find
useful. Unfortunately, at this time they are only available in English. Copies of
documents with EPA document numbers may be obtained from EPA Center for
x Environmental Research Information (CERI) or the Pollution Prevention Information
Clearinghouse (PPIC). Copies of documents with Pollution Prevention Information
Exchange System (PIES) numbers may be obtained through PPIC/PIES.
EPA CERI Publications Unit PPIC' PIES .
26 West Martin Luther King Drive 401 M Street" Technical Support Office
Cincinnati, OH 45268 Mailcode PM221A SAIC . '
(513)569-7562 ; Washington, D.C. 20460 7600-A Leesburg Pike '.
(202)260-1023 Falls Church, VA 22043 .
- '".' : (703)821-4800
GENERAL INFORMATION:
1. Guides to Pollution Prevention: The Metal Finishing Industry
U.S. EPA Office of Research and Development
EPA/625/R-92/011
. October1992 . ,
2. Waste.Minimization in Metal Parts Cleaning . .
U.S. EPA Office of Solid Waste and Emergency Response
: EPA/530-SW-89-049 . -'.'.
. 1989 . ;,.-.' , ' " .'-.'. '.;
3. Waste Audit StudyMetal Finishing Industry
'".. California Alternative Technology Section and U.S. EPA
: PIES#005-073-A . , , . .
* 1988 . ' : : .:".' ''"' , , .
4. Waste Audit StudyPrinted Circuit Board Manufacturers , ' ,
California Alternative Technology Section and U.S..EPA ;
' PIES#005-006 , ,_' ' '
1987 . ' .. . -.'-
5. Source Reduction of Chlorinated-SolventsElectronic Products Manufacture and
Solvent Cleaning -..-. ' , . .- .
Metropolitan Water District of Southern California & The Environmental Defense Fund
PIES'#609-008-A and PIES #609-005-A
1990 " .'.'.--.. ' ',".'. ' .-.
- 6. Facility Pollution Prevention Guide
U.S. EPA Off ice of Research and Developnnent - .
EPA/600/R-92/088 , . -,"-. , ; ,
May 1992--;'-"-' ; ,'- -..- ' - . ;
MACHINING
7: J. T. Johnson, Cincinnati Milacron Products Division. "A Comprehensive Strategy for an
Overall Program of Metal Working Fluid Management". Cincinnati, OH,1985.
SURFACE PREPARATION X
8. R. Schecter and G. Hunt, North Carolina Pollution! Prevention Pays Program. "Case
Summaries of Waste Reduction by Industries in the Southeast". Raleigh, NC. 1989. .
, Page 40. (PIES #112-003-A)
APPENDIX A
-------
SOLVENTUSAGE
9. L. Traverse, Massachusetts Office of Safe Waste Management. "Creative Source
Reduction Techniques". Third Annual Massachusetts Hazardous Waste Source
Reduction Conference Proceedings. Boston, MA. October 23,1986. (PIES #022-012)
10. R. Schecter and G. Hunt, North Carolina Pollution Prevention Pays Program. "Case
Summaries of Waste Reduction by Industries in the Southeast". Raleigh, NC. 1989.
Page 39. (PIES #112-003-A) .-...''
11. C. H. Fromm, S. Budaraju and S. A. Cordery, Jacobs Engineering Group. "Minimization
of Process Cleaning Waste". Solvent Waste Reduction Alternatives Seminar, Speaker
Papers. Washington, DC. March 1988. (PIES #005-012-A-OOO)
12 E A Rodzewich. "Source ReductionParts Cleaning". Solvent Waste Reduction
Alternatives Seminar, Speaker Papers. March 1988. (PIES #005-012-A-OOO)
13. Jacobs Engineering Group, Inc.-for (U.S. EPA), Hazardous Waste Engineering
Research Laboratory, Office of Research and Development. Waste Minimization Audit
Report: Case Studies of Solvent Wastes from Parts Cleaning and from Electronic
Capacitor Manufacturing Operations. Cincinnati, OH. (PIES #010-003-A)
14. Institute for Local Self-Reliance. "Engine and Plumbing Parts Manufacture, Case Study
60", Proven Prof its from Pollution Prevention: Case Studies in Resource Conservation
and Waste Reduction, Volume II. Washington, D.C. 1989. (PIES #306-001 -A)
15. North Carolina Department of Environment, Health, and Natural Resources: Pollution
Prevention Program. Managing and Recycling Solvents in the Furniture Industry.
Raleigh, NC. May 1986. (PIE'S #034-018-A) '
16. Hackney, Pollution Prevention Challenge Grant Program, North Carolina Department -
of Natural Resources. "Pilot Study of Solvent Recovery for Use in Paint Equipment
Cleanup". December 1986. (PIES #034-050-A-000)
17. N. H. Frick and G. W, Gruber, PPG Industries, Inc. Solvent Waste Minimization by the
Coatings Industry. Pittsburgh, PA. March 1988. (PI ES #800-01)
18. California Department of Health Services, Alternative Technology Section, Toxic
Substances Control Division, Wasfe Audit Study: Automotive Paint Shops. January
1987. (PIES #005-005)
19. M. Drabkin and P. Sylvestri, U.S. EPA Hazardous Waste Engineering Research
Laboratory, Office of Research and Development. Waste Minimization Audit Report:
Case Studies of Minimization of Solvent and Electroplating Wastes at a DQD
Installation. Cincinnati, OH. 1989. (PI ES #101 -036-B)
. AQUEOUS CLEANERS
20. K. B. Patterson and D. E. Hunt, U.S. Air Force, AGMC/MAQSE, Newark Air Force
Base, OH. 'The Cyl-Sonic Gleaner: Aqueous Ultrafiltratiori Cleaning Using
Biodegradable Detergents". Process Technology '88: The Key to Hazardous Waste
Minimization, Air Force Logistics Command. Sacramento, CA. August 15-18,1988.
(PIES #100-100-0)
21. T. Smietana, Office of Safe Waste Management Trichloroethylene Elimination Case
Study: Electric Furnace #2 Bright Anneal Line Industrial Metals Department of Texas
Instruments, Inc.," Third Annual Massachusetts Hazardous Waste Source Reduction .
Conference Proceedirigs^October 23,1986. (PIES #022-012)
. x , , ' , i '
WASTEWATERS
22. Massachusetts Departmentof Environmental Management, Office of Safe Waste
Management. Preliminary Report: Phase I Source Reduction Activities, Southeast
Platers Project. Case'Study B. July, 1988. Page 3. (PIES #022 003-A)
WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
23. North Carolina Department of Naturalflesources and Community Development. .
"Water Conservation for Electroplaters: Counter-Current: Rinsing". Raleigh, NC. 1985.
(PIES #034-024A) - '"',-' -'.-.. ' :
24. North Carolina Department of Natural Resources and Community Development "Water
Conservation for Electroplaters: Rinse Tank Design". Raleigh, NC. 1985. (PIES #034-
, , 026A), . ' ' .--.. . "--..''';'" '-..'"
25. Office of Safe Waste Management, Massachusetts Department of Environmental
Management. 'The"Bobbins Company: Wastewater Treatment and Recovery System,
A Case Study." Raleigh, NC. 1985. (PIES #034-0266) , .
DECREASING
1 ' '' *
26: G. Hunt, North Carolina Department of Natural Resources and Community
Development. "Accomplishments of North Carolina IndustriesCase Summaries".
Raleigh, NC. January 1986, p. 22. (PIES #034-010)
27. Hazardous Waste Reduction Program of the Oregon^ Department of Environmental
Quality. 'The Tektonix Payoff". Salem, OR. June 1988. (038^303-A-OOO)
" 28. United Nations, Economic and Social Council,"Economic Commission for Europe.
"Compendium on Low- and Non-Waste Technology: Elimination of Chlorine by the Use
of Fumeless In-line Degreasing in the Aluminum Industry". Geneva, Switzerland. 1983.
(PIES #400-103) -
29. New Jersey Hazardous Waste Facilities Siting Commission, Hazardous Waste Source
Reduction and Recycling Task Force". A Study of Hazardous Waste Source Reduction
and. Recycling in Four Industry Groups in New Jersey. Newark, NJ. April 1 987. Case -
.. studyD4.1,p.30.-(PIES#031-001-A)'' . , ' . .
30. S. P. Evanoff, et. al. "Alternatives to Chlorinated Solvent DegreasingTesting,
Evaluation, and Process Design" Process Technology '88. Sacramento, CA. August
15-18, 1988. (PIES #10.0-100-D)
SURFACE TREATMENT AND PLATING
ELECTROPLATING . ... "
31. G. Hunt, et al., North Carolina Department of Natural Resources and Community
Development. "Accomplishments of North Carolina IndustriesCase Summaries".
Raleigh, NC. January 1986, p. 22. (PIES #034-010) ;
32. United Nations, Economic and Social Council, Economic Commission for Europe
"Compendium on Low- and Non-Waste Technology: A Low-Waste Electroplating
Process". Geneva, Switzerland. 1985. (PIES #400-125)
33. D. HuisinghvL. Martin,H. Hilger, N. Seldmars The Institute for Self-Reliance. "Proven
Profit from Pollution Prevention". Washington, D.C. 1985, Case Study 26, Page 103.
(PIES#3Q6r001-A) ,'-"''."
34. G. F. McBae. "In-Process Waste Reduction: fart 1 Enviroscope," Plating and Surface
Finishing, June 1988. .. , :
35. David Wigglesworth, et.al., Alaska Heatth Project. "Waste Reduction Assistance
Program (WRAP)pn-Srte Consultation Audit Beport: Electroplating Shop". Anchorage,
Alaska. April 7,1987, pp. 17.-(PIES #002-016-A-001)
36. Edward Saltzberg, Ph.D., Science Applications International Corporation. "Methods to
Minimize Wastes From Electroplating Facilities", Process Technology '89: The Key to'
^Hazardous Waste Minimization, Air Force Logistics"Command. Sacramento, CA. /
August 15-18,1988. (PIES #100-100-D)
APPENDIX A
-------
37. Hubbard Enterprises, San Diego County, Department of Health Services. "Minimizing
Waste from an Electroplating Operation", Pollution Prevention, A Resource Book for
Industry. San Diego, CA. 1990. (PIES #005-079-A-000)
38. Jerome Kohl, et. al., North Carolina State University,'School pf Engineering. "Reducing
Hazardous Waste Generation with Examples from the Electroplating Industry*. Raleigh,
NC. 1986.
39. Office of Safe Waste Management, Massachusetts Department of Environmental
Management. "Source Reduction Recommendations for Precious Metal Platers."
Boston, MA. 'April 1988. (PIES #002-012) - .,
ELECTROPLATINGCHROMIUM
40. D. Achman, Minnesota Technical Assistance Program. "Reducing Chromium Losses
from a Chromium Plating Bath", Minnesota Technical Assistance Program Summer
Intern Report. Summer 1987. (PIES #709-030) ;
41'. United Nations Economic and Social Counsel. "Use of an Evaporator in Chromium
Electroplating", Compendium on Low- and Non-Waste Technology. Monograph ENV/
Wp.2/5/Add.47. Geneva, Switzerland. 1988. (PIES #400-125)
ELECTROPLATING-CYANIDE-CONTAINTNG WASTES
42. L. E. Vaaler. Office of Safe Waste Management. "Prospects for Developing Substitutes
for Cyanide-Containing Electroplating Baths", Third Annual Massachusetts Hazardous
Waste Source Reduction Conference Proceedings. Boston, MA. October 23,1986.
(PIES #022-012)
43. U.S. EPA Research and Development, Risk Reduction Engineering Laboratory.
"Waste Minimization Audit Report: Case Studies of Minimization of Cyanide Waste
from Electroplating Operations", Project Summary. Cincinnati, OH. January 1988. .
(PIES #101-023-6)
,i ' -' '
ELECTROPLATINGNICKEL
44. Minnesota Technical Assistance Program. Metal Recovery: Metal Finishing Shop.
Minneapolis, MN. September 1988. (PIES #709-017)
45. P. Pajunen, Eco-Tech Ltd., and E. Schneider, Hewlett Packard, American
Electroplaters and Surface Finishing Society and U.S. EPA. "Copper and Nickel
Removal in Printed Circuit Board Processing by Ion Exchange and Electroforming",
Ninth AESF/EPA Conference on Environmental Control for the Metal Finishing
Industry. January 25-29,1988.
46. T. Nadeau, et. al. "Copper, Nickel and Chrome Recovery in a Jobshop to Eliminate
Waste Treatment and Sludge Disposal", Third Annual Massachusetts Hazardous
Waste Source Reduction Conference Proceedings, Office of Safe Waste Management.
Boston, MA. October 23,1986. (PIES #022-012)
, 47. Minnesota Technical Assistance Program. Metal Recovery: Ion Exchange.
Minneapolis, MN. September 1988. (PIES #709-019)
48. T. V. Trah, et al. "Recovery of Nickel Salts by Electrodiafysis Reversal Process,"
Presented at 73rd Annual AESFTechnical Conference and Exhibit of Surface
Finishing. The American Electroplaters and Surface Finishers Society Bulletin: TP 334-
ST. June 23,1986. (PIES #222-001-A-001)
' X ' ' '
ELECTROPLATINGGALlMIUM
49. North Carolina Pollution Prevention Program. "Potential Recovery and Reuse of
Cadmium from an Electroplating Bath". Pollution Prevention Challenge Grant Program.
Raleigh, NC. December 1987. (PI ES #034-050-A-000)
i.
WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
FT FCTROPLATINGZINC , .
:50 Hazardous Waste Reduction Program, Oregon Department of Environmental Quality.
Guidelines for Waste Reduction and Recycling: Metal Finishing. Electroplating. Printed
Circuit Board Manufacturing. Eugene, OR. Jyly 1989. (PIES #038-010) -
; -* . -
51: Tom Nadeau, et.-a'l. "Copper, Nickel and Chrome Recovery in a Jobshop to Eliminate
Waste - . ;, . ' ,. ,
52. Treatment and Sludge Disposal", Third Annual Massachusetts Hazardous Waste
Source Reduction Conference Proceedings, Office of Safe Waste Management.
..Boston, MA. October 23, 1986. (PIES #022-012) ,
CONTINUQUS HARDENING '
53. United Nations, Economic and Social Council, Economic Commission for Europe.
"Compendium on Low- and Non-Waste Technology: Continuous Hardening and Zmc-
Goating"."Geneva, Switzerland, 1981. (PIES #400-103)
ZINC COATING
54. United Nations, Economic and Social Council, Economic Commission for Europe
"Compendium on Low-and Non-Waste Technology: Continuous Hardening and Zinc-
Coating". Geneva, Switzerland, 1981. (PIES #400:103) ' ' '
BRITE DIP BATHS
55. institute for Local Self-Reliance. "Engine and Plumbing Parts Manufacture, Case
Study 60", Proven Profits from Pollution Prevention: Case Studies in Resource
, : Conservation and Waste Reductionf Volume II. Washington, DC. 1989. (PIES #306-
,001-A) ' ' . .
ETCHING
56. Minnesota Technical Assistance Program, University of Minnesota. "Metal Recovery:
' Etchant Substitution". Minneapolis, MN. 1989/(PIES #709-014-A-OOO)
57. A. Boyce, Tekronix, Inc. and D.-Ji Kavanaugh, CH2M Hill Industrial Design
Corporation. "Electrolytic Regeneration of Chromic/Sulfuric Acid Etchant," Ninth AESF/;
EPA Conference Environmental Control for the Metal Finishing Industry. Americaa
Electroplaters and Surf ace .Finishing Society and U.S. EPA, Washington, DC. January
25-29,1988. / ' ' ' ;
58. V. R. Sellers. "Waste Management Alternatives forElectroplatirig and Printed Circuit-
Board Manufacturing Operations'", Third Annual Massachusetts Hazardous Waste
Source Reduction Conference Proceedings, Office of Safe Waste Management.
Boston, MA,pctober 23, 1986.-(PIES #022-012)
69. Thaddeus Srnietana. 'Tnchlofoethylene Elimination Case Study: Electric Furnace #2
Bright Anneal Line Industrial Metals Department of Texas lnstruments,.lnc.", Third
Annual Massachusetts Hazardous Waste Source Reduction Conference Proceedings,
Office of Safe Waste Management. Boston, MA. October 23,1986. (PIES #022-012)
CHROME CONVERSION
60. New. Jersey^Hazardous Waste Facilities Siting Commission, Hazardous Waste,.
Source Reductiori and Recycling Task ForceN'A Study of Hazardous Waste Source
Reduction and Recycling in'Four Industry Group's in New Jersey", Case Study 06.1,
p.33. Newark, NJ. April 1987. (PIES #031 ^001-A) ,
APPENDIX A
-------
61. K. Weigel. "Developments in Powder Coating Technology", Metal Finishing. April
1989. pp. 41-44. " ,
62. D. S. Tyler, -Volstatic, Inc. "Electrostatic Powder Coating: Finishing for the Future",
Metal Finishing, January 1985, pp.. 23-26. ,
63. Hans Sutler, Umweltbundesamt. "Low-Waste Technologies in the Federal Republic of
Germany", The Environmental Professional, Volume II, pp. 190-198. Berlin, Germany.
1989. (PIES #458-006-A-001)
64. North Carolina Department of Environment, Health, and Natural Resources: Pollution
Prevention Program.' Managing and Recycling Solvents in the Furniture Industry, May
1986. (PIES #034-018-A) ,
65. Hazardous Waste Reduction Program of the Oregon Department of Environmental
Quality. 'The Tektonix Payoff. Salem, OR. June 1988. (PIES #038-003-A-000)
66. Mark Manzione, Brown and Caldwell Consulting Engineers. "Waste Minimization for
Electroplating and Aircraft Paint-Stripping Wastewater Treatment", Process
Technology '88: The Key to Hazardous Waste Minimization, Air Force Logistics
Command. Sacramento, CA. August 15-18, 1988. (PIES #100-100-0)
67. Hackney. Pollution Prevention Challenge Grant Program, North Carolina Department
of Natural Resources. "Pilot Study of Solvent Recovery for Use in Paint Equipment
Cleanup". Raleigh, NC. December 1986. (PIES #034-050-A-000)'
68. California Department of Health Services, Alternative Technology Section, Toxic
Substances Control Division. Waste Audit Study: Aiitomotive Paint Shops.
Sacramento, CA. January 1987. (PIES #005-005) -
69. United States Environmental Protection Agency, Hazardous Waste Engineering
Research Laboratory, Office of Research and Development Waste Minimization. Audit
Report: Case Studies of Minimization of Solvent Waste from Parts Cleaning and from
Electronic Capacitor Manufacturing Operations. Cincinnati, OH. November 1987. (PIES
S101-008-A).
WASTE -MINIMIZATION IN THE METAL flNISHING INDUSTRY
-------
;:-
-------
;.v^--yvv',.V-?:.; SC .-.;
''"'vl \'-^>£v'i>:£-
-------
INTRODUCTION
The production of economically competitive products is the?driving force behind
any successful business. Quite often the manufacturing process requires the use
of various chemicals. The purchase and storage of these chemicals, their use in
the process, and the ultimate disposal of the waste created by the manufacturing
process can present many problems. These problems include financial concerns,.
: as well as issues associated with environmental management and worker health
and safety. Pollution prevention occurs when action is taken to reduce the waste
created by manufacturing processes. It includes practices that reduce the use of
hazardous and nonhazardous materials, energy, water, and other resources, as
: well as those practices that protect natural resources through conservation or
-more.efficient use.
Because of the enormous potential for pollution prevention along the United States
and Mexican border, the U!s. Environmental Protection Agency and SEDESOL
established a Pollution Prevention Workgroup in February 1990 to promote and
coordinate the reduction of. pollution through a broad range of approaches:
! * technical assistance, training, public and private sector pollution prevention
awareness programs, assessment of pollution prevention opportunities, policy
development and institutional support, and technology development and
investment activities. -
The purpose of this first manual is to provide pollution prevention information for
the metal finishing industry. The manual will be expanded in the future to include
other industries that are typical in the border area, such as the chemical
- manufacturing and wood finishing industries. The manual contains the following
sections. ,
Section I The Goals and Benefits of Pollution Prevention
In this general introduction/the term "pollution prevention" is clarified. This
section also includes an overview of the benefits of applying pollution preven-
tion techniques.
Section II Waste Minimization in the Metal Finishing
, Industry
This technical section contains descriptions of various processes associated
with the metal finishing industry and pollution prevention options for that indus-
try: This section may be of particular interest to process engineers.
Sectional CaseStudies
This section includes specific examples of companies that have used pollution
prevention techniques. These case studies describe the benefits, particularly
cost savings, these companies have achieved. . .
-
INTRODUCTION
-------
Attachment A Information on Accessing Pollution
Prevention Information Clearinghouses
This section describes how to access the International Cleaner Production
Information Clearinghouse (ICPIC) database, which is an international cleanng-
house for pollution prevention information.
Attachment B Survey
PLEASE COMPLETE THE SURVEY INCLUDED IN THIS SECTION. Your
response provides valuable information for evaluating the usefulness of this
manual. Additionally, by mailing in the survey, your name will be placed on a
mailing list for updates to the manual and other documents as they become
available.
Appendix A Referencing Additional Information
This section lists additional technical documents pertaining to pollution preven-
tion opportunities for the metal finishing industry, and other information. Cur-
rently these documents are available in English only.
SECTION 1: THE GOALS AND BENEFITS OF POLLUTION
PREVENTION
The goal of a pollution prevention program is to minimize all waste P^1^ .
PoHuUon prevention includes any action a company takes to reduce the amount of
waste created by a manufacturing process prior to recycling, treatment, or disposal
of the waste. To effectively accomplish this, the program must be an ongoing,
comprehensive assessment of the operations at a facility.
pFMFFITS OF A POLLUTION PREVENTION PROGRAM
Both businesses and governments have strong incentives to reduce the toxicity' _
andI aheervahma of the waste they generate. The cost of Pi^lucngefdmrt w,ll
decrease as pollution prevention measures tower operating costs. Therefore,
companies with an effective, ongoing pollution prevention plan will have a
significant competitive edge.
The overal benefits of a polluttori prevention program, discussed in more detail
betow, include the following:
protecting human health and environmental quality
Reducing operating costs - \
m Improving employee morale and participation
Enhancing your company's image in the community
Reducing the potential for penalties and fines
WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
PROTECTING HUMAN HEALTH AND ENVIRONMENTAL
QUALITY
Reducing the waste released to air, land, and water will help the environment and
protect human health. Typical harmful, pollutants that can be reduced significantly
by pollution prevention techniques include the following:
Air emissions solvent fumes, fine.particulates, 'and carbon monoxide
Land disposal heavy metarsludge, waste solvents, and debris
Water disposal wastewater contaminated with heavy metals, cyanide, and
other toxic materials ;' " '' '.
The health and safety of employees can be affected by poor ventilation, ,
mishandling of chemicals, and a lack of proper safety equipment. An informative
employee training program is an important way to reduce accidents. Reducing the
amount of chemical materials and wastes at a facility is also beneficial because it
reduces the 'amount of space required for storage as well as the potential for
accidental spills. Furthermore, there may be a reduction in hazardous waste
transportation requirements if the volume of pollution is minimized.
REDUCING OPERATING COSTS
An effective pollution prevention program can yield cost savings that will more than
offset program development and implementation costs. Cost reductions may be
immediate savings that appear directly on the balance sheet or anticipated savings
based on avoiding potential future costs. Cost savings are particularly noticeable
when the costs resulting from the treatment, storage, or disposal of wastes are
allocated to the production unit, product, or service that produces the waste.
Materials costs, or the costs to purchase materials,1 can be reduced by adopting
production and packaging procedures that consume fewer resources. This
approach uses resources more efficiently and creates less waste. As wastes are
reduced, the percentage of raw materials converted to finished products
increases, this leads to a proportional decrease in materials costs.
Waste management and disposal costs may be reduced when less waste is
produced. Required procedures for proper handling of the waste at the facility, as
well as specific treatment, disposal and transportation methods ^re typically labor
intensive and very costly. These requirements and the associated costs are
expected to increase.
Production costs can be reduced through a pollution prevention assessment.
When people examine production processes from a fresh perspective, they find
opportunities for increasing efficiency that might not otherwise have been noticed.
Production scheduling material handling, inventory control, and equipment
maintenance are all areas where facilities can work to reduce the production of
waste of all types, arrf thus control the cx>sts of production.
Energy costs will decrease as the facility implements pollution prevention
measures in various production lines. In addition, companies can reduce the
energy used to operate the overall facility by doing a,thorough assessment of how
operations interact. - "x
INTRODUCTION
-------
IMPROVING EMPLOYEE MORALE AND PARTICIPATION
Employees are likely to feel better about their company when they believe that.
management is committed to providing a safe work environment and is acting as a
responsible member of the community. By participating in pollution prevention
activities, employees have an opportunity to be part of a "team," and interact
positively with co-workers and management. Helping to implement and maintain a
pollution prevention program should increase each employee's sense'of
commitment to company goals..This positive atmosphere helps to retain a
competitive work force and to attract high-quality new employees. '.
ENHANCING THE COMPANY'S IMAGE IN THE COMMUNITY
The quality of the environment has become an issue of greater importance to
society. Your company's policy and practices for controlling waste increasingly
influence the attitudes of the community at large.
Community attitudes are more positive toward companies that operate and
publicize a thorough pollution prevention program. If a company creates
environmentally compatible products and avoids excessive use of material and
energy resources, the company's image will be enhanced in both the community
and with potential customers and consumers.
REDUCING THE POTENTIAL FOR PENALTIES AND FINES
Mexico's environmental laws include administrative penalties that entitle
government inspectors to require temporary or permanent closure of businesses
that are out of environmental compliance. A clearly written pollution prevention
plan that includes standard operating procedures that comply With environmental
laws and regulations is very helpful. By following the plan, a company is less likely
to incur any violations and associated penalties.
WHAT IS POLLUTION PREVENTION?
, Pollution prevention (also known as "source reduction" and."waste minimization")
is any action that reduces the production of wastes (at their source) that may be
otherwise released to the air, land, or water. There are two general methods to
achieve pollution prevention: (1) process changes and (2) product changes.
Various source reduction changes are summarized in Figure 1.
Process changes allow resources to be more efficiently used during the '
manufacturing process. These changes include the following:
Prudent purchasing, where the most appropriately sized container of new
material is bought, rather than buying too much and having to dispose of the
unused portion
Operational changes, such as reuse of input materials during production and
reduction of water consumption in the process lines
Technology changes, such as using a safer process material
Increase in energy efficiency
WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
Figure 1 - Source Reduction Methods
Sourc« Reduction
_L
Product Change*
Design for less environmental impact
Increase product life
_L
Input Material Changes
Material purification
Substitution of less
toxic materials
Process Changes
Improving Operating
Practices
i Layout changes
i Increased automation
i Improved operating
condrtions
i Improved equipment
i New technology
Technology Changes
Operating and
maintenance
' procedures
Management practices
Stream segregation
Material handling
improvements
Production scheduling
Inventory control : ;
Training
Waste segregation
Rgure 2 provides morespecific examples of process changes.
Product changes reduce the volume of pollution when the finished product has
less of an impact on the environment during the manufacturing phase, as well as
the uhimate use and disposal of the product. Product changes can indude the
following:
Development of a toss chemical-intensive product
Development of a higher-quality product that lasts longer
Incorporation of a life-cycle analysis, which includes the use and disposal
options for the product
OTHER ENVIRONMENTAL MANAGEMENT STRATEGIES
There are a number of. pollution control measures that are applied only after
wastes are generated. They are, therefore, not correctly categorized as pollution
prevention! Figure 3 provides some examples of procedures that are waste
management measures;
It should be emphasized that transferring hazardous wastes to another
environmental medium is not pollution prevention. Many waste management
practices to date have simply collected pollutants and moved them from one
environmental medium to another. For examplte^solvents can be removed from
wastewater by means of activated carbon adsorbers. However, regenerating the
INTRODUCTION
-------
Figure 2 - Process Change Methods
The following process changes are pollution prevention measures because
they reduce the amount of waste created during production.
The following are examples of input material changes:
Stop using heavy metal pigment.
Use a less hazardous or toxic solvent for cleaning or as coating.
Purchase raw materials that are free of trace quantities of hazardous or
toxic impurities. '
The following are examples of technology changes:
Redesign equipment and piping to reduce the volume of material con-
tained, cutting losses during batch or color changes or when equipment is
drained for maintenance or cleaning.
Change to mechanical stripping/cleaning devices to avoid solvent use.
Change to a powder-coating system.
Install a hard-piped vapor recovery system to capture and return vapor-
ous emissions.
Use more efficient motors.
Install speed control on pump motors to reduce energy consumption.
The following are examples of improved operating practices:
. Tram operators.
Cover solvent tanks when not in use.
Segregate waste streams to avoid cross-contaminating hazardous and
nonhazardous materials.
Improve control of operating conditions (e.g., How rate, temperature,
pressure, residence time, stofchtometry).
Improve maintenance scheduling, record keeping, or procedures to
increase efficiency.
Optimize purchasing and inventory maintenance methods fot input
materials. Purchasing in quantity can reduce costs and packaging mate-
rial if care is taken to ensure that materials do not exceed their shelf We.
Reevaluate shelf life characteristics to avoid unnecessary disposal of
stable items.
Stop leaks, drips, and spills.
Turn off electrical equipment such as lights and copiers when not in use.
Place equipment soaato minimize spills and losses during transport of
parts or materials.
Use drip pans and splash guards.
WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY'
-------
Figure 3 - Other Environmental Strategies
The following are other environmental management strategies:
Off-site recycling: -
Off-site recycling (for example, solvent recovery at a central distillation
facility) is an excellent waste management option. However, it does create
pollution during transport and during the recycling procedure.
Waste treatment: ,
Waste treatment involves changing the form or composition of a waste
stream through controlled reactions to reduce or eliminate the amount of
pollutant. Examples include detoxification, incineration, decomposition,
stabilization, and solidification or encapsulation.
Concentrating hazardous or toxic constituents to reduce volume:
Volume reduction operations, such as dewatering, are useful treatment
approaches, but they do not prevent the creation of pollutants. For ex-
ample, pressure filtration and drying of a heavy metal waste sludge prior to
disposal decreases the sludge water content and wastevolume, but it
does not decrease the number of heavy metal molecules in the sludge.
Diluting constituents to reduce hazard or toxicity:
Dilution is applied to a waste stream after generation and does not reduce
the absolute amount of hazardous constituents entering the environment.
Transferring hazardous or toxic constituents from one environmental
medium to another:
Many waste management, treatment, and control practices used to date
have simply collected pollutants and moved them from one environmental
medium (air, water, or land) to another. An example is scrubbing to
remove sulfur compounds from" combustion process off-gas.
carbon requires the use of another solvent or heating, transfering the waste to the
air. In some cases, transfer is a valid treatment option. However, too often.the
purpose has been to shift a pollutant to a less-tightly regulated medium, In either
case, media.transfers are-not pollution prevention.
Off-site recycling is vastly preferable to other forms of waste handling because it
helps preserve raw materials and reduce the amount of. material that will require
disposal. However, compared with closed-bop recycling (or reuse), performed at
the production site, off-site recycling is likely to have more residual waste that
requires disposal associated with it. .Furthermore, waste transportation and the
recycling process carry the risk of worker exposure and release to the
environment. , ' N._ -
Waste treatment prior to disposal reduces the toxicity and/or disposal-site space
requirements but does not eliminate all pollutant materials. This includes such
processes as volume reduction, dilution, detoxification, incineration, stabilization,
and other measures. . -&, , . ,
INTRQDUCnON
-------
The pollution prevention hierarchy, represented on Rgure 4, prioritizes waste
management options from those that are most environmentally beneficial to those
that are least environmentally beneficial. More specific technical information on
pollution prevention options for the metal finishing industry is found in Section II of
this manual.
Figure 4 - Pollution Prevention Hierarchy
Pollution Prevention Source Reduction
Recycling and Reuse
Treatment
\
8
WASTE MINIMIZATION IN THE METAL FINISHING INDlfSTRY
-------
SECTION II
Waste
Minimization
for the Metal
Industry
-------
\
-------
,.--.'-'-: - : ' ' (((lf{ffl((ff((fffffffffff
WASTE MINIMIZATION
ASSESSMENT PROCEDURES
MODULEIII
WASTE MINIMIZATION IN THE METAL
FINISHING INDUSTRY
A JOINT PROJECT OF
UNIVERSITY EXTENSION
UNIVERSITY OF CALIFORNIA, RIVERSIDE
ALTERNATIVE TECHNOLOGY DIVISION
CALIFOFtNIA DEPARTMENT OF TOXIC SUBSTANCES CONTROL
,' UNITED .STATES-'..
ENVIRONMENTAL PROTECTION AGENCY
, AUTHORS:
JON W. KINDSCHY, M.B.A.,CHWS
UMVERSITY OFCAUFORMA EXTENSIOH, UNtVERSTY OF CAUFORMA, MVERS106
DAVID RINGWALD, B.S.
PROJECT DIRECTOR:
MOLLY CARPENTER, M.A.T.
COMTtNUtNG EDUCATION SPEOAUST
UMVERSITV OFCAUFORNU EXTENSION, UNIVERSITY OF CAUFORMA. »VERSID£
MAY 19 91
-------
\
-------
ACKNOWLEDGMENTS
SPECIAL THANKS TO:
Reviewi
Kathryn Barwick, California Environmental Protectfon Agency, Department of
Toxic Substances Control, Office of External Affairs, Office of Pollution
Prevention and Technology, Development, Sacramento
Dave Hartley, California Environmental Protection Agency Department of Toxic
Substances Control, Office of External Affairs, Office of Pollution Prevention
and Technology Development, Sacramento
Robert Ludwigs, California Environmental Protection Agency, Department of
Toxic Substances Control, Office of External Affairs, Office of Pollution
Prevention and Technology Development, Sacramento
Andora Sprecher, Comtox Corp., Big Bear City, California
Kim Wilhelm, California Environmental Protection Agency, Department of Toxic
Substances Control, Office of External Affairs, Office of Pollution Prevention
and Technology Development, Sacramento
Par Formatting and Graphics;
. Shelley Hall, Publications Department, UCR Extension
Jack Van Hise, Publications Department, UCR Extension
PROJECT ADVISORY COMMITTEE MEMBERS ;
John Aubert, General Dynamics, Pomona Division.
Al Crane, General Dynamics, Pomona Division i
Cathy Godfrey, Bourns Incorporated, Riverside
Jon Kindschy, University of California Extension, Riverside
Marilyn Kraft, County of San Bernardino, Department of Environmental Health
Services .
Robert Ludwig, California Environmental Protection Agency, Department of
Toxic Substarvces Control, Office of External Affairs, Office of Pollution
Prevention and Technology Development, Sacramento
Michael Mettzer, Lawrence Livermore Lab, University of California, Berkeley
Steve Mercer, formerly with Rohr Industries, Riverside
JudyOrttung; County of San Bernardino, Department of Environmental Health
Services .
Mike Shetleri Riverside County Health Department, Hazardous Materials
Branch ."'.''. ;..-'.' --',".,
Donna Toy-Chen, Board of Public Works, Hazardous arid Toxic Materials
Project, Los Angeles v '
' - - - ' ' ', - "' . ' ^"v," " " -"
Linda Verhoeven, Rohr Industries, Riverside V
Janet M. Weder, Seven W Enterprises and Highland Supply Corp., Redlands
ACKNOWLEDGMENTS
-------
DISCLAIMER
The statements and conclusions of this report are those of the Regents of
the University of California and not necessarily those of the State of
California or the U.S. Environmental Protection Agency. The mention of ,
commercial products, their sources, or their use in connection with
material reported herein is not to be construed as either an actual or
implied endorsement of such products.
DISCLAIMER
n - ' .
-------
^ ' (MMIMMW
CONTENTS :. . \V ; . . ' -.'.
INTRODUCTION AND PURPOSE ........*..... 1
CHAPTER!. DESCRIPTION OF METAL FINISHING
SYSTEMS
Metal Cleaning and Stripping ,...... .3
Organic Solvent Cleaning .......: 5 .
Aqueous Based Cleaning 6
Abrasive and Thermal Methods .......... - 6
.'Surface Treatment and Plating 8
Chemical and Electrochemical Conversion 9
Electroplating and Related Processes .....10
Metallic Coatings......... :....;......... ,..,.....;..... ...10
Case Hardening ...., .....:...-....;:..<: 10
Printed Circuit Board Manufacturing 11
CHAFTERZ WASTE MIMMIZAHON OPTIONS FOR THE
METAL FINISHING INDUSTRY \
Source Reduction in Cleaning and,Stripping. .. 13
Preventing the Need for Cleaning -13
Solvent Source Reduction ..- - 14-
Aqueous-based Wastes . .-.-..»...'. 14-
Abrasives Source Reduction..,.. ............/....I............... 15
Source Reduction in surface Plating and Related Processes.............. 15
ProcessSubstitution...........;.........;. ....;....'.....:...- 16
Material Purchase, Storage and Handling .........i... . :......,........:..:. 16
Avoiding Material Degradation. ..» 16
ManagingjSamples ,..^..... :..;............. .;............ 16
. Spills ....S»............ ....: ...:....: .............<;. 18
Residue^ and Empty Containers. 18
Inspections .............;%.-.. 18
ProcessBaths ;:.'................:!....;'.'...:. 18
Material Substitution .....:.... .,........;.. ^.. ..:.... 18
Extending Solution Life ; 19
Drag-Out Reduction ...........,...:...................\.... 20
" Rinse Systems-; .;...' ';.. ........4.,...;:. ..;............ 22
Improved Housekeeping ...:.................,.. 22
- * - » " ' ,.- f '
-CONTENTS '' ' . ' .;: ' '"' .'-' ,'.- . *"
-------
Source Reduction in Printed Circuit Board Manufacturing , 22,
Product Substitution r ' 24
Cleaning and Surface Preparation 24
1 Electroplating and Electroless Plating 24
Pattern Printing and Masking 24
Etching .....24
Recycling and Resource Recovery in Cleaning and Stripping 25
Solvent Recycling '. : 25
Aqueous-based Cleaner Recycling - 25
Recycling & Resource Recovery in Surface Plating & Related Processes . 26
Material Recovery and Reuse 26
Evaporation 26
' Reverse Osmosis - 26
Ion Exchange - -.....,... 27
Electrolytic Recovery - 28
Electrodialysis 28
Rinse Water. Reuse 28
Recycling and Resource Recovery in Printed Circuit Board Manufacturing 28
Review Questions ,. - 31.
References ' » 33
Glossary 35
WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
INTRODUCTION AND PURPOSE
This booklet is part of a project to develop training materials for
waste generator inspectors. The three training modules address -
aspects of waste minimization.
, This module outlines the processes involved in metal cleaning, metal
finishing, and printed circuit board manufacturing and the potential for waste
minimization within each of these activities. However, the applicability of
waste minimization strategies to a particular shop will vary significantly .
depending on such variables as floor space for new equipment, utility service
. capacity contractual specifications, or restrictions on wastewater discharge.
Thus a realistic evaluation of waste reduction potential must include
. qualitative information as well as a quantitative evaluation of the costs and
benefits of proposed changes. . . _
This module is intended to provide the key concepts necessary to familiarize
the inspector with the scope of the metal finishing industry arid the search for
viable waste minimization options: It will describe the two major categories
of metal finishing operations, metal cleaning and stripping, and surface
treatment and plating. An allied industry, printed circuit board manufacturing,
will also be discussed. Strategies for reducing waste will include examples
of source reduction, recycling and reuse.. Economic factors which act as
both a driving force for and a barrier against waste minimization will also be
discussed. The glossary provides definitions of terms related to the subject
beyond those used in this module. _,.
Accompanying this Module is a Department of Health Services publication '
: Waste Reduction Chprklist & Ass^f?""* Manual for the
entitled:
i Finishinn Industry. It is available in quantity for distribution to metal
finishers as inspections are completed. Section 1 of the booklet provides a
checklist of waste minimization opportunities which parallels the discussion
in this workbook. Section 2 of the booklet provides a series of tables for
evaluating the potential applicability of the options discussed in this manual.
The inspector should be thoroughly familiar with the Department ofHealth
Services booklet as well as Modules I and ll.of this training senes. Thus, the
inspector will be prepared to assist the operators of the .facilities inspected in
their waste minimization opportunity assessments.
Module III is intended to augment the information in the .Department of
Health Services booklet and to provide you, as an inspector, with the
technical background to understand the related processes to maximize your
effectiveness in enforcing regulations and in contributing to the goals of the
State in reducing the volume and tox.icity of our industrial waste stream.
Reduce
Volume
Reduce
toxicfty
.\
INTRODUCTION AND PURPOSE
-------
WASTE MINIMIZATION IN THE MEWL FINISHING INDUSTRY
-------
This chapter will:
Review the metal finishing processes of cleaning and stripping1 and the
processes of treatment and plating
Review the printed* circuit manufacturing process
Chapter 1
DESCRIPTION OF METAL
FINISHING SYSTEMS
There are approximately13,000 metal finishing and printed circuit shops in
the United States. The U.S. Environmental Protection Agency (EPA)
estimates that in i986 the metal finishing industry generated 129,000,000
gallons of metal-bearing waste. The industry includes a vast array of
.manufacturing facilities. The size of operations ranges from small "mom and
pop" shops, which only use a few processes and typically do contract work
for larger companies, to very large operations, which have many finishing
' lines using dozens of processes and have hundreds of employees. Almost
all of these companies have installed wastewater treatment systems to
comply with the Clean Water Act. As a result, these companies generate ,
toxic metal sludges that are regulated pursuant to Resource Conservation
and Recovery Act. Compliance with these two federal laws, in addition to
other state, county and local regulations, can require industry to spend 10 to
15 percent of their sales dollar on compliance. Compliance with the landfill
ban has caused disposal costs to increase by 25 to 150 percent. These
facts of life for the metal finishing industry make waste minimization a high
priority.
Large and
small shops
contribute to
waste streams
METAL CLEANING AND STRIPPING
The objective of metal cleaning and stripping is simply to clean both metallic
and non-metallic surfaces in preparation for subsequent processes. This
generally involves removing contaminants such as rust, paint, old plating
and a wide variety of "soils". Removal of soils can be achieved by means of
using detergents, solvents, chemical reactions, or mechanical action. In
surface treatment and plating operations processes are used to impart
particular characteristics to a material, such as reducing surface reactivity;
increasing corrosion resistance, strength or conductance; or producing
desired textures-or colors. Both chemical and mechanical processes are
used to accomplish these objectives and both produce waste materials
containing metals and other chemicals, which must be disposed of properly.
Metal finishing often involves many steps, and there can be cohsiderable
periods of time between the steps. To protect the metal workpieces over
these intervals, they are often coated with oils or paints to prevent oxidation
from occurring while in storage or in transit. Prior to continuing with the next
step, these protective coatings must be removed. Also, workpieces that
must be handled pick up traces of body oils arxfother soils that can interfere
DESCRIPTION OF METAL F/N/SR/NC SYSTEMS
-------
MMl.llimii
The cleaning
process
selected
depends upon
the form of
contamination
with subsequent processing steps. Traditionally, organic solvents have been
used to remove these materials. These solvents do not add to the metal-
bearing waste load from metal finishing, but they are considered to have
significant human health.and environmental risks. This stems not only from
their toxicrty, but also from their ftammability and resistance to biodegradation.
Industrial cleaning costs in the metal finishing industry are considerable, but the
costs of improper or incomplete cleaning of surfaces prior to plating can be even
higher. For example, early failure of moving engine parts has been traced to
inadequate surface cleaning, which resulted in excessive wear. The. primary
cause of the failure of paint and plating to properly adhere is that they were
applied to a soiled surface.
The cleaning methods vary considerably depending on the type and quantity of
the soil, the nature of the base metal and the coating material, as well as the
shape of the workpiece and its end use. A cleaning process that proves
adequate for subsequent anodizing of steel would be totally unsuitable if the
same workpiece were to be nickel plated.
In the cleaning process, four forms of contamination must be considered. They
are grease soil, loosely adherent soil, adherent soil and moisture. A typical
workpiece may have a combination of these soils.
Grease soil - Includes normal lubricating oils, oils used during machining,
grease used for protection of components during storage and natural oils in
fingerprint contamination.
Loose soil - Includes, dust and fine turning and grinding debris from
machining. These are often found in conjunction with machining oil. This
form of contamination can be compared to chalk on a chalkboard in that the
particles adhere loosely to the surface.
Adherent soil - Commonly includes scale or rust, but might also include
bumed-on oil or paint that has served its purpose and needs to be removed.
Moisture - Normally present in the atmosphere, it may appear as
condensation on .workpieces or come from machining with water-soluble oils.
This ubiquitous contaminant can also be blamed for some of the adherent
soils described above. .
Each of these types of contaminants and the methods for removing them will be
discussed in subsequent sections. It should, however, be reemphasized that a
single form of contamination will seldom be found in practice. A series ,of
cleaning operations is generally required to fully prepare a metal surface for its
final treatment. The order in which the workpieces move through the cleaning
processes depends on the types of soils present.
In these processes soils are removed using four different means: 1) solvent
' action, 2) detergent action, 3) chemical reaction, and 4) mechanical action.
Some of these may be employed in combination to increase the effectiveness of
others. For example, ultrasonic vibration, a mechanical action, is commonly
used in conjunction with both solvent-based and aqueous-based baths to
increase their cleaning efficiency.,
\
WASTE MINIMIZATION IN THE METAL FINISHING INDUSTTKf
-------
ORGANIC SOLVENT ACTION Describes the ability of one material
(solvent) to easily make a mixture with another material (solute). For the
purposes of this discussion the solvent and solute are both non-aqueous-
based. ' : : .
DETERGENT ACTION Describes a substance or mixture of substances
that removes a soil from a surface and maintains it in aqueous solution.
Detergents are generally composed of surfactants or alkaline salts and
caustics, individually or in combination. Surfactants are surface-active
agents that promote the removal of contaminants from a surface.
Emulsion cleaners combine surfactants and solvents.
CHEMICAL REACTION Changes the target soil chemically (e.g.,
oxidation, reduction) by using chemical or electrochemical processes
such that the soil is removed from the metal surface and retained in
solution. , .
MECHANICAL ACTION Direct contact with a solid material under force;
or, in the case of ultrasonic vibration, high frequency sound waves .
through a liquid medium, to remove the target soil. This includes wiping,
polishing and blasting.
There are three primary cleaning processes used for metals: 1) organic
solvent cleaning, 2) aqueous-based cleaning, and 3) abrasive and thermal
methods.
ORGANIC SOLVENT CLEANING
Solvent cleaning describes the use of solvent to remove oil and grease from
surfaces. This can be accomplished in a number of ways, including the
simplest, wipe cleaning, where a cloth is moistened in a solvent and rubbed
across a surface. Although still in practice for some heavily soiled
workpjeces, its effect can be to spread soils to areas that are not.
contaminated. The same can be said for immersion cleaning where a rack
of workpieces is immersed in a bath of solvent. The bath quickly becomes
contaminated with the soil so when the rack is withdrawn and the solvent
evaporates, a film of soil evenly coats the surface.
The classical method for the removal of oil and grease from a surface is
vapor degreasing. It usually consists of boiling a solvent cleaner, generally
one of the chlorinated hydrocarbons, resulting in the heated vapor phase,
into .which the contaminated workpieces are inserted. The vapor phase then
condenses on the cold components to produce a clean hot solvent, which
dissolves the oil and grease. As further solvent condenses, h removes the
dissolved soils.,, . .
Historically, the industry has used carbon tetrachloride and other solvents .
such as benzene for solvent cleaning. These have now been shown to
constitute significant health risks and have been removed from the
workplace. The most commonly used solvents now in use are 1,1,1 -
trichloroethane (TCA), trichloroethylene (TCE), perchloroethylene (PERC),
and methylene chloride (METH). The last three solvents named are rapidly
disappearing from use for several reasons, including ozone depletion. In
particular, trichloroethylene, a carcinogen, has been increasingly replaced
with substitutes such as methanol and acetone." ,
Metal
cleaning
methods
DESCRIPTION OF METAL FINISHING SYSTEMS
-------
AQUEOUS-BASED CLEANING
Aqueous cleaning comprises a wide range of water-based cleaning methods
that use detergents, acids, and alkaline compounds to displace soil rather than
dissolving it in an organic solvent. Aqueous cleaning has been found to be a
viable substitute for many metal finishing operations currently using solvents.
Alkaline and acidic cleaners are applied using soak cleaning, spraying,
ultrasonic cleaning, electrocleaning, and steam cleaning. The principal
advantages of aqueous-based cleaning are the ease of treating spent solutions
by pH adjustment and generally good biodegradability of organic detergents
used in alkaline baths. Its principal disadvantage is that the workpieces are wet
after cleaning and ferrous parts easily rust under these conditions unless they
are dried rapidly. A common technique to accomplish this is hot water rinsing,
but this is a more costly alternative. Another disadvantage associated with
aqueous-based cleaning is an increase in the chemical oxygen demand (COD)
of the wastewater and wastewater treatment costs. Mild steels are difficult to
clean effectively in an aqueous process.
About half of the approximately 100 million tons of steel produced in the U.S.'
every year is treated in acid pickling baths. In this process sulfuric acid
(H2SO4) or hydrochloric acid (HCI) is used to remove scale from the
surface of the raw ingot, sheet, or rod. Acidic cleaning solutions may
contain other mineral acids such as nitric or phosphoric; organic acids
such as acetic, citric, oxalic, or sulfamic; detergents; chelating agents; and
possibly small amounts of solvents. This process removes up to 1.5
percent of the metal and dissolves it in a pickling liquor (the acid with the
dissolved scale). As the iron content of the bath increases, the pickling
efficiency of the bath decreases to the point where new acid must be
added or the dissolved iron must be removed. When the steel is rinsed, .
residual acid and dissolved metal are "dragged out" into the rinse water, creating
another waste stream. Three waste streams are created by the pickling
process: spent pickling liquor, rinse water and metal sludge from acid recovery.
Alkaline cleaning solutions (usually run hot) are comprised of builders and
surfactants. Builders usually consist of sodium salts of phosphate (PO4),
carbonate (CO3), silicate (SiO4) and hydroxide (OH ). Their function is to
promote chemical reactions which will remove the metal oxides from the surface
of the workpiece. Surfactants are detergents and soaps that tie up the metal
oxide, and cause it to remain in the solution and not recombine with the metal
surface. Other additives are often used in conjunction with builders and
surfactants to act as anti-oxidants and stabilizers. Some shops use an
electrolytic cleaning method. All methods require a final rinse step after
cleaning.
ABRASIVE AND THERMAL METHODS
Mechanical means of cleaning can be an effective alternative to aqueous
cleaning. Abrasives can be used in tumbling barrels or applied to buffing wheels.
Abrasive blast cleaning methods use plastic, ceramic, or sand blast media to
clean and strip parts. The blast media can be recycled, thereby reducing
disposal costs. Acid oc alkaline cleaners are sometimes added to form abrasive
slurries in order to improve cleaning action. These slurries are discharged after
a set period of use, but require controls for total dissolved solids (TDS) in the
wastewater. . . '
WASTE MIN1MIZAT10N IN THE METAL FINISHING INDUSTRY.
-------
Heat or flame cleaning/stripping ovens offer another method of removing
paint and other organic soils fronf workpieces by burning them off. The
disadvantages of heat cleaning are high energy requirements, and the
production of combustion emissions, which require control devices. Refer to
Table 1 for a summary of primary cleaning processes.
Table 1 - PRIMARY METAL CLEANING PROCESSES
PROCESS ,
Solvent cleaning .
'Aqueous-based
cleaning -
\s - '
Abrasive- . ' '
Thermal cleaning
MATERIALS
1.1.1- '
Trichloroethane
methanol, &
acetone
Detergents; caustic
& acidic
compounds
(NaOH, H2SO4)
Grit, sand, ceramic
and plastic media;
Heat
HOW USED
Vapor degreasing,
immersion, wiping
Heated tanks,
spraying, steam
cleaning, &
ultrasonic cleaning
Grinding, tumbling,
blast cabinets;
Burn*off ovens
"/x
DISADVANTAGES
High material
costs; worker
exposures & ,
flammability
High COD &TDS
in wastewater;
creates metal
sludges '
High capital costs,
APC equipment
required
High energy costs,
APG equipment
required ,
" "-
DESCRIPTION OF METAL F/N/SH/NC SYSTEMS
-------
Illllillllllllllillll!!!!
Modifying
the metal's
surface
SURFACE TREATMENT AND PLATING
Surface treatment and plating operations are typically batch processes in which
metal workpieces are dipped into and then removed from baths containing
various reagents. The reagents are specially formulated to achieve the required
surface condition. The workpieces can be carried on racks or in barrels that
rotate in the plating bath.
Most surface treating and plating processes consist of three steps. The first is
cleaning or preparation of the surface, which has already been described. The
second step is the actual modification of surface itself, which involves some
change in the properties of the surface. The final step is the rinsing of the
workpiece. Metal-bearing waste is generated from alt three of these processes.
Four surface modification processes are listed below in Table 2.
Table 2 - PRIMARY SURFACE TREATMENTS
PROCESS
DESCRIPTION
CHEMICALS USED
Chemical &
electrochemical
conversion
Deposition of a metal
oxide coating, for
corrosion resistance
and primarily to form an
absorptive base for the
adhesion of paints, etc.
Phosphates, chromates,
nitric acid, hydrochloric
acid, and metal coloring
Electroplating &
related processes
Metallic coatings
Workpiece acts as an
anode or a cathode in a
galvanic cell. Metal
ions are either attracted
to the part and plate
out, or are removed for
a high shine.
Dipping the core piece
into molten metal;
through vapor
deposition and vacuum'
coating
Brass, bronze,
cadmium, chromium,
copper, iron, nickel, tin,
zinc and precious
metals
Aluminum, tin and zinc
Case hardening
Produces a hard
surface over a soft core
metal by chemical
diffusion or rapid heat
application
Carbon (carburizing),
nitrogen (nitriding),
(using a salt bath of
sodium and potassium
cyanide)
8
WASTE MINIMIZATION IN THE MfTAL FIN/SHINC INDUSTRY
-------
rHFMICALAMD FT.ECTROCHEMICAI CONVERSION
Chemical and electrochemical conversion treatments include phosphating,
chromating, anodizing, passivation, and metal coloring. These treatments
deposit a metal oxide coating on the metal surface, which is primarily
intended to form an absorptive base for the adhesion of paints, lacquers,
and oils applied in subsequent processes, the cpatings also impart some
corrosion resistance to the surface. See Figures 1 and 2 for illustrations of
chromating of aluminum and steel passivation.
PART
ALKALINE CLEANER
HEATED 120-laO-F
WATER RINSE
UNHEATED
ACIOOESMUTTEH
UNHEATEO
WATER RINSE
UNHEATEO
IRFSOITE P90CESS
UNHEATEO
RINSE WATER
HEATED 12O-180-F
ALUMIN01* SURFACE PHEP/UUTON-DIP TANK ONE
nCUREl
A
WATER
. . - B ' '
NITRIC ACID/WATER
' C
WATER:
STAINLESS STEEL SURFACE PREPARATION (PASSIVATION)
DIP TANK LINE
Figure 2 x
DESCRIPTION OF METAL FINISHING SYSTEMS,
-------
llliilillitllillllllllll!
EKevolyt*
ELECTROPLATING AND RELATED PROCESSES
in electroplating, a workpiece is the equivalent of a cathode in a galvanic cell. It
is placed in a solution of the dissolved metal to be plated. The electric potential
applied across the cell is sufficient to attract the metal ions to the cathodic
workpiece where they are reduced on the surface. Metals which are commonly
electroplated onto workpieces are brass, bronze, cadmium, chromium, copper,
iron, nickel, tin, zinc and precious metals such as gold, platinum and silver.
In electropolishing, the workpiece acts as the anode. Surface metal is then
oxidized and dissolved in the bath solution. High points on the metal surface
dissolve faster than recessed areas. The result is a brightly polished surface.
METALLIC COATINGS
There are several nonelectrical techniques for applying a metal to a core of
another metal. Frequently, aluminum, tin, or zinc is applied by dipping the core
piece into a molten bath of the coating material. The high heat condition results
in coating adherence through a lattice interdiffusion of the two metals. Cladding
techniques bond the coated metal through high pressure, welding, or casting.
Other techniques include vapor deposition and vacuum coating. See Figure 3
for a graphic showing vapor deposition of aluminum.
CASE HARDENING
This process produces a hard surface over a relatively soft metal core. The
processes harden the surface through diffusion of carbon (carburizing). nitrogen
(nitriding), or carbon and nitrogen (carbonitriding) into the steel surface.
Nitriding involves the use of ammonia or a salt bath comprised largely of sodium
cyanide and potassium cyanide. Alternatively, nonchemical processes achieve
case hardening through very rapid heat application, which acts on the carbon
already present within the workpiece.
Substrate
Holder
Cathode
Evaporator
Power
Supply
High Voltage
Power Supply
Aluminum
Evaporators
"\
Vacuum
Chamber
A Vapor Deposition of Aluminum
Figure 3
10
WASTr, MfNlM17.ATKW IN THE METAl: F/N/SH/NC INDUSTRY
-------
a
an
a
PRINTED CIRCUIT BOARD MANUFACTURING
Many aspects of printed circuit board manufacturing are very similar to
processes used in electroplating. The circuit board consists of a x
nonoonductive material laminated with copper foil. Holes are then drilled
and deburred to allow for wiring and electrical component connection. The
board is then plated with electroless copper to approximately seventy
millionths (0.000070) of an inch thickness. This serves as the base for
electrolytic copper which is plated to an approximate thickness of one
thousandth (0.001) of an inch, or one mil. Then gold, lead, nickel or tin is
electroplated, followed by the etching of the circuit pattern onto the board.
Chemicals used in the manufacture of printed circuit boards include chromic
acid cupric chloride, and ferrous chloride for etching; stannpus tin
compounds and palladium chloride for catalysts; copper sulfate for
electroless plating; copper pyrophosphate, acid-copper sulfate. ac'dcopper
fluoroborate, tin-lead, gold and nickel solutions for electroplating; and suKunc
dichromate for resist stripping. Refer to Table 3 for a list of materials and
their components. -
Table 3'- CHEMICALS USED IN THE MANUFACTURE OF PRINTED CIRCUIT BOARDS
Product/Process Raw Material
an
aai
gL
a aaa
.Board materials
Cleaners
Etchants
Catalysts
Electroless copper bath
Screen v
Screen Ink
Resists
Sensitlzers
Resist solvents
Electroplating
Resist stripping
glass-epoxy. ceramics, plastic, phenolic paper,
copper foil
sulfuric acid, fluoroacetic acid, hydrofluoric acid,
sodium hydroxide, potassium-hydroxide,
trichloroethylene, 1.1.1-trichloroethane.
perchldroethylene, methylene chloride
sulfuric and chromic acid, ammonium persulfate,
hydrogen peroxide, cupric chloride, ferric
chloride, alkaline ammonia
stannous chloride, palladium chloride
copper sulfate, sodium carbonate, sodium
gluconate; Rochelle salts, sodium hydroxide,
formaldehyde ' : '
silk polyester, stainless steel composed of oil,
cellulose, asphalt, vinyl or other resins
polyvinyl cinnamate, ally! ester, resins,
isoprenoid resins, methacrylate derivatives.
polyolefin sulfones
thiazolirie compounds, azido compounds, mtro
compounds, nitro aniline derivatives, anthones.
quinones, diphenyts, azides. xanthone. benzil
ortho-xylene, meta-xylene, para-xylene, _
toluene, benzene, chlorobenzene, cellosolve and
cellosolve acetate, butyl acetate, 1,1.1.-
trichloroethane. acetone, methyl ethyl ketone,
methyl isobutyl ketone.
copper pyrophosophate solution, acid-copper
sulfate-solution, acid-copper fluorobate solution,
tin-lead, go^ld. and nickel plating solutions
suituric-drchromate, ammoniacal hydrogen
peroxide, solutions methachlorpperbenzpic.acid,
methylene chloride, methyl alcohol, furfural,
phenol, ketones. chlorinated hydrocarbons, non-
chlorinated organic solvents, sodium hydroxide
DESCRIPTION OF METAL F/N/SH/NG SYSTEMS
11
-------
JJ2 WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
This chapter will:
Outline source reduction techniques used in:
metal cleaning and stripping
surface plating and related processes
printed circuit board manufacturing
Outline recycling and recovery processes used in:
metal cleaning and stripping
surface plating and related processes
printed circuit board manufacturing
Chapter 2 ,
WASTE MINIMIZATION OPTIONS FOR
THE METAL FINISHING INDUSTRY
Least Desirable
SOURCE REDUCTION IN CLEANING
AND STRIPPING
If workpieces must be cleaned, the least hazardous material
. should be considered first. Ideally, the cleaning method of choice
would involve the fewest number of steps, employ the the least
toxic medium, and generate the least waste. The most desirable
cleaning media are air and water/ If these are not effective,
abrasive media with air or water as carriers are the next most
desirable. These may be applied by either hand wiping or with a
blast-type device that uses pressure. -
If chemicals are required to achieve the necessary finish, they should be
tried in the following order: aqueous detergent solutions, alkaline solutions,
acids, and solvents. This hierarchy is based on the hazardous properties of
the options and treatment costs. Many aqueous .detergents can be
discharged directly to a POTW without treatment. Effluent containing
aqueous detergents will often meet POTW discharge requirements without
additional treatment unless metal contamination is excessive. When
treatment is required, it is usually for total dissolved solids (TDS) or chemical
oxygen demand (COD). Alkaline solutions typically require only pH
adjustment before discharge,. Acid solutions can have considerable metal
content and must therefore be treated more extensively. Solvents present'a
number of problems, including their flammability hazard and health risks to
workers. Before a shop changes from one cleaning process to another it
should fully evaluate the effects of the new cleaner, such as the effect of g
substitute cleaner's surface residue or drag-out, on downstream processes.
The shop should also check with its local air district to make sure that this
use of the splvent is permissible. - .
PREVENTING THE NEED FOR CLEXNING
The first step in implementing this very desirable option is to identify the type
of surface soil. A wide variety of materials is used in order to facilitate the
cutting, grinding, and drawing of metal parts. These include mineral oils,
Solvent
Acid
Alkaline
Detergents
Abrasives
Air & Water
Most Desirable
WASTE MINIMIZATION OPTIONS FOR THE METAL FINISHING INDUSTRY
13
-------
iliillillllillilillilllll
Substitute
non-hazardous
coatings
Substitute
alkaline
cleaners
Extending the
useful life of
the cleaning
solution bath
talc, graphite, chlorinated synthetic oils, and metallic soaps. Workpieces may
also be coated with water scale, heavy metal salts, or simply covered with
rust. Metal finishers should be encouraged to explore other fess hazardous
materials to facilitate these operations.
Metal finishers should be encouraged, to establish a "just' in time" approach to
manufacturing, where parts are cleaned in batches ho larger than can be
immediately fed into subsequent processes. This eliminates the need to
warehouse parts between operations, during which they may contact new
contaminants and need to be cleaned again. If cleaned parts must be stored,
dry nitrogen bagging is a proven way to keep parts clean and free of oxidation
as they are stored for subsequent coating.
Some coatings are applied by vendors supplying the workpieces to the metal
finisher These coatings are intended to protect the material, bufthey simply
add another waste stream when they have to be removed. The metal finisher
should work with the vendor to replace the coating with a nonhazardous peel
coating or shrink wrapping with polymeric sheeting.
It should be emphasized, however, that although the avoidance option should
be examined first, unwarranted relaxation of cleaning requirements may have
an opposite effect of increasing waste generated due to rework of rejects
caused by poor coating.
SOLVENT SOURCE REDUCTION
Halogenated compounds are the. solvents typically used in cleaning
operations' These compounds are known to pose significant environmental
health hazards and should be used' only when an alternative aqueous-based
emulsion, or mechanical cleaning method is not feasible. If non-solvent
cleaning is not possible, the use of alternative, less hazardous solvents such
as terpenes, N-methyl-2-pyrrolidone, or dibasic acid esters should be
considered.
The use of hot alkaline cleaners can prove a viable substitute for solvent
degreasing. The purchase price for alkaline cleaners can be as little as half
that of solvents. Treatment and disposal costs are also generally lower for
alkaline cleaners: Some need only pH adjustment before discharging to a
publically-owned treatment works (POTW). Others may require treatment for
excessive TDS or COD. Other alternatives to solvent cleaning are discussed
below, with the emphasis on minimizing their waste output.
-RASra WASTES
While aqueous-based cleaning methods are superior to solvents,
consideration should first be given to the use of water, steam, or abrasives as
substitutes for acid or alkaline cleaners. If their use is not feasible, then work
with the shop operator to evaluate each aqueous-based cleaner with an eye
toward selecting the cleaner that is least hazardous to workers and the
environment. .
Regardless of the aqueous-based cleaning method selected, a key to
achieving waste minimization goals is to. extend the useful lifetime of the
cleaning solution bath. It & critical to ensure that workpieces entenng the
cleaning solution are as free of oils, solvents, or other cleaners as possible A
hot water bath for precteaning may be desirable. The bath should be supplied
14
WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
with demineralized water, possibly from the last rinse bath of the cleaning
.operation. . , ; ' ' : ,-, ,-/
The accumulation of metal fines and paint chips is detrimental to aqueous-
based cleaning solutions. Continuous filtering or regular sludge removal
should be used to prolong the useful life of the solution. Tanks should have
plastic liners or be coated with protective finishing to eliminate the entrance
of impurities from the tank itself into the cleaning solution. The racks and
barrels used to hold the workpieces should be corrosion-free so that rust is
not added to the cleaning solution and excess drag-ouHrom solution
adherence to roughened surfaces can be avoided. '
Float valves, while important to maintaining the proper level in the tank,
should be closely monitored to ensure that leaks are not diluting the bath.
. The effectiveness of alkaline cleaner baths is reduced by introduction of
materials that reduce the alkalinity, including the target soil. Bath life can be
enhanced by avoiding unnecessary loading with .hard water or carbon
dioxide in the air used for agitating the tank. Mechanical agitation and the
use of softened or deionized water are solutions to these problems. The
operator should also consider keeping the tank heated continuously to
minimize the absorption of carbon dioxide, with occasional cooling to allow
for oil removal. . .-
ABRASIVES SOURCE REDUCTION
Oil-based binders can burn due to the heat of friction generated during
buffing This results in the need for additional cleaning to remove the
burned-on oil. As an alternative, greaseless compounds, if used properly,
will result in parts which are clean and dry after buffing. These greaseless,
buffing compounds also prolong wheel life by adhering to the surface of the;
wheel.
The technique used for applying liquid spray abrasives to the buffing wheel
can make a significant difference in waste generation. Too little will result in
excessive wheel wear, while over-application will produce waste compound
and create the need for further cleaning of the workpiece. The use of a
spray gun for applying liquid abrasive spray has proven to be the most
effective technique-in controlling the application rate.
Maintaining the proper water level in mass cleaning operations is critical to
source reduction. If not enough water is used, parts will leave the solution
dirty. Excessive water flow will increase the attrition rate of the abrasive and
increase replacement frequency. , ;
Using
greaseless
buffing
compounds
SOURCE REDUCTION IN SURFACE PLATING AND
RELATED PROCESSES
There are significant opportunities for waste reduction by metal finishers.
When changes are first suggested the inspector may encounter resistance to
change by some metal finishers. "If it's not Brpken, why fix it", can be a
common response from them when aiternative'chemistries or operating
procedures are suggested. Witlvwaste disposal costs skyrocketing it may
WASTE MINIMIZATION OPTIONS FOR THE METAL FINISHING INDUSTRY
15
-------
Change to
less
hazardous
processes
be just such an attitude that results in going broke. The primary goal is to
challenge the metal finisher to initiate a review of his operation. Success stories
of others can be extremely helpful. The bibliography contains references for
numerous case studies.
PROCESS SUBSTITUTION
Plating operations are inherently more dangerous to the environment than many
other metal coating techniques. It is not likely that the inspector will get involved
in rethinking the entire process used by a finishing shop, but one should
generally be aware of potential process substitutions such as buffing, cladding,
and electroless coating, some of which were introduced in the previous section
titled "metallic coatings". Also, some accepted material substitutions to reduce
or eliminate the toxicity of the waste are referred to in Table 4.
MATERIAL PURCHASE. STORAGE- AND HANDLING
Proper control over the chemicals used in the finishing process is an important
way to reduce waste generation. This can be accomplished by establishing
material purchase and control procedures. As one of the first steps in an
inspection, the inspector should determine the extent to which the metal finisher
has established procedures relating to the purchase of chemicals. For instance,
it is important that all material purchases be reviewed" by a key individual or
group within the operation prior to purchase. The approval process should
determine if the materials being evaluated contain hazardous constituents. If
so. the cost of treating and disposing of the waste generated s.hould be
determined and added to the cost of purchase. This will help the facility to
evaluate the total costs of purchasing a chemical before the purchase is made.
Many substitute materials may have a higher purchase price than presently
used materials, but disposal and treatment costs may be lower. The inspector
should encourage the metal finishing facility to use a "cradle to grave"
philosophy when evaluating the purchase of all materials.
Avoiding Material Degradation
Hazardous materials that have deteriorated due to prolonged storage or
materials held beyond their shelf life must be managed as hazardous wastes.
You should encourage metal finishers to review their inventory and material
usage policies of the finisher. Suggestions may include strict tracking of
inventories, minimizing the volume of materials in inventory, and adopting a first-
in first-out material usage policy. ,- .
Limiting employee access to raw materials is likely to reduce careless waste.
The assignment of responsibility for mixing Chemicals for process baths to a
limited number of employees will ensure batch consistency, thereby reducing
waste.
Managing Samples
The metal finisher should ask chemicalsuppliers for small samples of less
hazardous replacement chemicals. The metal finisher should also arrange.in
advance with the chemical supplier to return the unused portion of the sample,
since it must be managechas a hazardous waste. A bench scale test of the
sample may be run to determine the quality of the final finish before any large
scale tests are run. Many-alternative products may need to be tested before an
adequate replacement is found. Bench scale tests make the screening process
16
WASTE M/N/M/Z/mO.V IN THE METAL FJN/SH/NC INDUSTRY
-------
Table 4 - CHEMICAL SUBSTITUTES
POLLUTING
Fire Dip (NaCN)
Heavy Copper Cyanide
Plating Bath
Chromic Acid PickleSi
Deoxidizers, & Bright
Dips
"Chrome-Based
Anti-Tarnish
"Cyanide Cleaner
Tin Cyanide
Plating with Chromic
Acid
Hydrofluoric Acid in . ;
Pickling and Stripping
SMBSTITUTE
Muriatic Acid with
additives
Copper Sulfate
.- S '
/ ,
Sulfuric Acid and
Hydrogen Peroxide
Benzotriazole (0.1-i.0%
olution in methanol) or
water-based proprietaries
Trisodium-Phosphate or
Ammonia
Acid Tin Chloride
Plating with trivalent
chromium, or bright nicke
Proprietary Fluoride Salts
COMMlNTS
Slower acting than +^2^2
traditional fire dip.
Excellent throwing power
with a bright, smooth,
rapid finish. A copper
cyanide strike may still be
necessary for steel, zinc,
or tin-lead base metals.
Requires good pre-plate
cleaning. Noncyanide
process eliminates
carbonate buildup in
tanks.
Nonchrpme substitute,
Nonfumjng.
Nonchrome substitute.
Extremely reactive,
requires ventilation.
Noncyanide cleaner.
Gooti degreasing when
not and in an ultrasonic
bath. Highly basic. May
complex with soluble
metals if used as an
intermediate rinse
between plating baths
where metal ion may be
dragged into the cleaner
and cause waste water
treatment problems.
Works faster and better
that the polluting
chemical.
Reduces worker
exposures to more
hazardous hexavalent .
chromium.
Reduces worker, hazards
WASTE MINIMIZATION OPTIONS FOR THE MEWL FINISHING INDUSTRY
17
-------
much easier and less expensive. Plus, valuable production time is not lost and
large numbers of workpieces can be reworked if the candidate chemistry does
not produce acceptable results.
Spills
The best way to reduce spill-generated wastes is for the shop to have a training
program for personnel in proper handling of materials and appropriate
procedures for handling spills. Simple techniques such as the use of spouts,
funnels, and drip pans during material transfer can have a significant cumulative
impact, Shops can place "collars" or drainboards that direct drainage back into
the process bath to eliminate spills to the floor. Providing adequate freeboard,
the distance between the top of the tank and the liquid level in the tank, can
reduce overflows in process tanks. Liquid spills may be best cleaned up
through use of a mop and wringer rather than being soaked up with an
absorbent, which must then be transferred off site for treatment or disposal.
However, spills must be compatible with the mop, and mop and other clean-up
tools must be kept segregated. Spill containment berms should also be
suggested for areas of high spill probability.
Spills resulting from equipment failure can be prevented through strict
adherence to preventive maintenance programs.
Residues and Empty Containers
Controlling access to raw materials and instituting a check-in procedure for
empty containers will result in the complete use of one container of a chemical
prior to the opening of another. In this manner residues will be minimized and
container rinsing, if appropriate, will be ensured. Otherwise, empty containers
can be readily gathered for return to the manufacturer, avoiding their accidental,
and possibly illegal, deposit into the solid waste receptacle. Unfortunately, many
suppliers will not take containers back. Try to get a commitment from suppliers
to take empty containers back before purchasing.-
Inspections
Successful implementation of the suggestions in this section depends upon,
close monitoring by the shop manager. A key element in this monitoring is a
regularly scheduled inspection.program. The-inspection should include
examination of all equipment, piping, chemical storage areas, chemical
containers and labels, training records, and chemical inventory records.
PROCESS BATHS
Material Substitution
Chemical chelators are used in many processes to increase the solubility of
metals in the bath. Included in this class of compounds are organic acids such
as citric acid, maleic acid and oxalic acids and amines, such as EDTA. In
alkaline solutions these chemicals have a strong affinity for metal ions and they
are able to support higher concentrations of metals in solution. The problem
with these chemistries is the large volume of sludge produced when they are
treated. The first step in the treatment of chelated process chemistries is to
adjust the pH to between 3 and 5. This inactivates the chelators so the metal
ions may be precipitated. This is generally done by adding ferric sulfate in a
18
WASTE MINIMIZATION IN THE METALflNISHINC INDUSTRY
-------
ratio of up to eight to one by weight to the contaminating metal. The volume
of sludge generated is thus increased eight-fold over that of the contaminant
alone. - " '. . . .
Non^helated chemistries are an alternative you might suggest to the metal ,
finisher The cost of these non-chelated materials is slightly higher than' the
cheiated alternative, but the sludge volume generated is significantly lower
The non-chelated chemistry usually requires continuous filtration, which will
cost between $400 to $1000 per tank, plus filter replacements and
maintenance costs. For this modest investment the metal finisher will
reduce waste and lower treatment costs, and the treated effluent is more ;
likely to meet POTW discharge requirements-.
The health risks of hexavalent chromium are well documented. Its treatment
as a waste requires the addition of sodium metabisulfite to reduce it to the
trivalent state. Cost savings have been demonstrated through the direct
plating of trivalent chromium. This process has proven especially viable for
decorative chrome plating. The most significant drawback to this system is
that the plated pieces tend to have a darker and less shiny appearance than
hexavalent plated pieces. On balance, though, the disadvantages of this
substitution are outweighed by the advantages which include decreased
liability, lower disposal costs and increased worker safety.
One of the most hazardous materials used by the metal finishing industry is
cyanide. Inspectors finding this material in general use should suggest that
- alternative chemistries be sought by the facility. When disposal of the
cyanide-bearing baths is necessary, they are usually treated by alkaline
chlorination using hypochlorite salts or chlorine gas. If complex cyanides are
being treated, ferric sulfide must be used for precipitation with the previously
mentioned large volume of sludge being generated. Refer to Table 4 for
alternatives to hexavalent chromium and cyanides. >
Successfurnon-cyanide plating of zinc and copper has been demonstrated.
Research is focusing on the development of a practical non-cyanide
cadmium plating process. Economic incentives can make the change to
' non-cyanide chemistries extremely attractive to a metal finisher. A two
gallon per minute rinse water flow containing cyanide can require as much
as $12,000 in treatment equipment and $3.00 per.pound in treatment
chemicals. . ' , ,
Extending Solution Life ..' ,
Metal finishers should also consider methods of extending the life of process
baths as a waste reduction strategy. The longer a bath can be used, the
lower annual treatment and disposal costs will be, Deionized make.-up water
should always be. used in process tanks and rinse systems. The carbonate
and phosphate present in tap water reduce the efficiency of rinsing
operations and reduce the life of process baths. The solids in tap water also
increase the amount of hazardous sludge created. Deionizatton systems
consist of a series of steel tanks containing a mixed bed of resins. These
resins have active sites on their surfaces,'which have affinities for either
negatively charged anions or positively charged cations. As the tap water is
passed through the resins, ionic compounds are adsorbed by the resins,
thereby purifying the supply water. The cost for installation and rent of a
Using
de-ionized
make-up
water
WASTE MINIMIZATION OPTIONS FOR.THE METAL FINISHING INDUSTRY
19
-------
tiiiiiiiiiiiiiiiiiiiiiiii
Replenish
baths rather
than
dumping
"them
Remove
contaminants
from baths
deionization system will generally be offset by reduced costs resulting from
longer rinse bath lives.
One problem commonly found in alkaline baths is the build-up of carbonate
salts These come from the dissolution of atmospheric carbon dioxide in the
baths Accumulated salts, as well as other cleaning and etchant compounds,
can interfere with the efficiency of the process bath and reduce-rts useful life
Removal of these precipitates using continuous filtration can extend the useful
life of the bath and thereby reduce the waste produced annually from that
process.
Process baths are depleted in a number of ways. Chemicals essential to the
process are removed as drag-out coating workpieces; water evaporates from
' the bath and contaminating chemicals are introduced when workpieces are not
completely rinsed.. Replenishing the bath is one option the metal finisher should
consider before dumping the bath. This requires some simple monitoring
practices such as routine measurement of pH and metals concentration. When
the effectiveness of the bath falls off, part of the bath can be dumped and fresh
water and chemicals can be added to replace what has been lost.
The introduction of contaminants cannot be controlled by simply adding more
water and chemicals. Eventually, the levels of contaminants will increase to the
point where process efficiency will begin to be affected. It is at this point that the
finisher should be encouraged to seek out a treatment process that can extend
the life of the bath. For example, copper can contaminate zinc and nickel
plating baths. When this happens some platers will use a treatment process
called electrolytic dummying. This process relies on the fact that the
contaminant copper, has a lower electrolytic potential than the zinc or nickel in
the process bath. 'An electrolytic plate is placed in the bath and a very low
current is applied to it. Since the copper requires less electric potential to be
reduced it plates out preferentially on the panel. It can take several days to
reduce the copper contaminant to-acceptable levels, but the trade-off is the
extension of the bath's life and reduction in waste generation.
1 ',",''. , ' , . ' '
in another example, the "plater may take advantage of the extreme insolubility of
lead and cadmium sulfide salts. By simply adding ferric sulfide to the process
bath and tittering the resultant precipitate from the bath, the bath life can be
extended In all cases, the inspector should encourage metal finishers.to use
their special knowledge of their own processes to find new ways to extend the
useful life of their process baths. Periodic laboratory-analysis of process tank
contents will enhance understanding of the unique chemistries involved and
how to increase process solution life.
i ,
D,rag-Out Reduction
Reduction of drag-out from process baths is a key to reducing waste in the -
metal finishing industry. Drag-out occurs when process solutions adhere to
workpieces and are carried into subsequent rinse tanks. The drag-out creates a
waste stream that must then be treated. Reducing drag-out can save in both .
reduced process chemical costs and waste disposal costs.
The volume of drag-out is influenced by the size and shape of workpieces, the
viscosity of the process batr\and the concentration of the bath.
. Some workpieces have concave surfaces, which can trap considerable volumes
20
4HSTE MljiHMK/TON IN THE MEWL HNEH/NG INDUSTRY-
-------
of solution when they are withdrawn from a bath. The inspector should
observe the procedures the operators are using when the racks containing
the workpieces are removed from baths. Try:to determine if by simply
turning, twisting or shaking the racks, additional drainage of process
solution can be achieved. Also make certain that the time the racks
are allowed to drain over the tank is sufficient. Some metal
finishers have installed a rail over their process baths where
operators can hang racks to increase the drainage time. Also,
observe the rate at which the racks are withdrawn. The slower
the rate of withdrawal, the thinner the film of drag-out on the
. workpieces. '
The higher the viscosity of the bath,.the thicker the film
coating the workpieces will be. There are several ways the
metal finisher can reduce the viscosity and resultant drag-
out. Reducing the chemical concentration in the bath will not
only reduce viscosity, but also will reduce the costs of -
chemicals and of treatment when the bath is dumped. The inspector should
encourage the finisher to test tower chemical concentrations when process
baths are formulated to determine if this option is viable. If product quality is
reduced, the chemicals can be added in increments until the desired quality
is achieved. This may not be adoption if contractual specifications require a
minimum bath concentration. , . ' :
Another way to reduce the viscosity of process solutions'^ to increase the .
temperature. While temperatures can increase the effectiveness of some
cleaning, it can also pose a greater risk to workers through higher emissions
of toxic air contaminants, such as chromium and cyanide, and it will increase
energy costs.
When high temperature baths are used in conjunction with drag-out tanks,
the benefits can be doubled. A drag-out tank is a tank placed next to a
process bath and filled with deionized water. When the workpieces are
.withdrawn from the process bath and drained, they are placed in the drag-
out tank. The contents of the drag-out tank can eventually be used as make
up for the process tank either after an evaporation step is used to
concentrate the drag out tank solution, or directly. Drag-out tanks can
reduce rinse water volumes and chemical costs by as much as 50%.
Fog sprays and air knives are very useful in reducing dragrout. A spray of
deionized water or air can return as much as 75% of the drag-out back to the
process tank. Fog sprays are typically located just above, the surface of the
bath and work best where the rate of spray jnatches the rate of evaporation,
from the tank. Air knives, also located just above the tank, reduce the drag-
out by mechanically scouring the liquid adhering to the workpiece. However.
when using compressor-supplied air, it is important to properly filter the air to
prevent the contamination of the bath or .the part with oil; Further, in some
cases it may not be desirable for the workpiece to dry between process
steps. Both of these very effective drag-out reduction techniques can be
installed for about $500 per tank.
The use of wetting agents can reduce drag-out by up to 50%. The metal
finisher should ask his chemical supplier if wetting agents are used in the
chemistries being supplied and, if not, whether wetting agents can be added.
Allow longer
drainage
Use less
viscous baths
Other methods
for reducing
drag-out
WASTE MINIMIZATION OPTIONS FOR THE METAL FINISHING INDUSTRY
21
-------
Use
countercurrent
rinse systems
In some plating baths wetting agents'have been found to improve the quality of
the finish as well as reduce drag-out.
The manufacturers of the process chemicals may recommend concentrations
greater than are necessary to do a quality job. Maintaining baths at the lowest
acceptable concentrations will reduce the amount of drag-out. Fresh baths will
function at lower concentrations which can then be increased during
replenishment.
The inspector should try to impress upon the metal finisher that these drag-out
reduction measures, alone or in combination, are essential to an effective waste
minimization program and may in fact result in significant reductions in water-
usage and treatment costs.
KTNSF SYSTEMS
The focus of rinse system design and review is on the
conservation of wastewater. If the shop has sufficient floor .
space, the installation of a multi-stage counter-current rinse.
system can reduce water consumption up to 99%. This system
utilizes multiple rinse tanks, through which the workpiece is
dipped in succession. Fresh rinse water flows into the last of
the tanks. Overflow from each rinse tank flows into the tank up
the line, in the opposite direction of the movement of the
workpiece. Effluent from the uppermost rinse tank is used as
wat" make-up water for the process tank or captured for recycling,
resource recovery, or treatment.,
Whether or not multistage rinsing is used, spray rinsing prior to djp rinsing will
significantly reduce drag-out, thereby allowing a reduction in the rinse tank(s)
flow rate.
Agitation of rinse tank water or of the racks holding the workpieces also
increases the efficiency of the rinsing process.
Pre-set block valves or valves with restrictive orifices can bq used to control
water flow.
IMPROVED HOI ISF.KEEPING
Elimination of space between tanks or installation of drainboards to direct drag-
out back into the tanks when moving workpieces from one tank to another will
prevent drainage onto the floor, which would otherwise enter the floor drains
during hose down operations. .
SOURCE REDUCTION IN PRINTED CIRCUIT BOARD
MANUFACTURING
Due to-the similarities of many of the processes used in surface plating and
those used in printed circuit (PC) board manufacturing, this section focuses on
those aspects of source reduction unique to PC board manufacturing. For
additional information on^source reduction in cleaning and surface preparation,
v electroplating and electroless-Rlating. and rinse systems, refer to these sections
in the prior discussion of surface plating and related processes. Fable 5 lists
chemicals and subsequent wastestreams generated in the manufacture of PC
boards.
22
WASTt: MINIMI7AT10N IN'Tlir. MftAL fW/SWNC INDUSTRY
-------
TableS
WASTE SOURCE
WASTE STREAM
DESCRIPTION
WASTE STREAM
COMPOSITION
Cleaning/Surface
preparation
1. Airborne
particulates -
2. Acid fumes/organic
vapors
3. Spent acid/alkaline
solution
4. Spent halogenated
solvents
5. Waste rinse water._
Board materials, sanding
materials, metals,
fluoride, acids,
halogenated solvents,
alkali.
Catalyst application /
Electroless plating
1. Spent electfoless
copper bath ,
2. Spent catalyst
solution
3. Spent acid solution
4. Waste rinse water
Acids, stannic oxide;
palladium, complexed
metals, chelating agents.
Pattern
printing/masking
1 .Spent developing
solution
2. Spent resist removal
. solution
Vinyl polymers,
chlorinated hydrocarbons,
organic solvents, alkali.
,
Electroplating '
Etching
3. Spent acid solution
4. Waste rinse water
1 , Spent plating bath
2. Waste rinse water
1. Spent etchant
2. Waste rinse water
- -
Copper, nickel, tin,
tin/lead, gold, fluoride,
cyanide, sulfate.
;
Ammonia, chromium,
copper, iron, acids.
WASTE MINIMIZATION OPTIONS FOR THE METAL FINISHING INDUSTRY
23
-------
New products
being
developed
Use aqueous
resist and
screen printer
PRODUCT SUBSTITUTION
The conventional method for attaching components to a circuit board requires
that there be holes in the board. New developments in surface mount
technology allow for closer contact area of connected leads, thereby allowing a
reduction in board size to as little as thirty-five percent of the .conventional .
design. As board sizes are decreased, waste generation is decreased
commensurately, with the exception of degreasing agents such as CFC-113
which are required in significantly greater quantities to adequately clean the
boards for surface mounting. When an appropriate substitute for the ozone-
depleting CFC-113 is identified, the relative environmental impacts of this
technology should be less than those of the traditional technology.
Battelle has developed a technique which couples injection molding of the board
with a fast-rate electrodeposition technique that is used to produce a complex
circuit board without the need for etchants, thereby reducing waste generation.
CLEANING AND SURFACE PREPARATION
While it is possible to use chelators in printed circuit board manufacturing
process solutions to increase the solubility of metal ions, this practice has been
curtailed due to tighter controls on wastewater. When used, this practice results
in the need for additional reducing agents, such as ferrous sulfate, which cause
the generation of significantly more sludge. The use of non-chelate process
solutions or a mild chelator such as ethylenediaminetetraacetic acid (EDTA)
may be feasible. For etching, non-chelate etchants such as sodium
permanganate and hydrogen perdxide/sulfuric acid may be feasible, but their
use requires rigid controls. However, non-chelate process baths require
continuous filtration to control buildup of solids, a cost item the operator must
evaluate in comparison to waste management costs.
PATTERN PRINTING AND MASKING
The desired pattern on a circuit board is created by the application of a material
which resists plating. Such a material is called resist. Conventionally used
resist must be'processed and developed with organic solvents. Aqueous
processable resist is available which results in decreased waste generation.
Screen-printing of circuit patterns instead of photolithography is recommended
to eliminate the need for developers. New high-resolution screen-printing
techniques have increased the potential applicability of this alternative
approach.
Etching
The potential tor using thinner copper foil should be explored. This alternative
reduces the copper load produced during the etching process.
Explore the use of non-chelated etchants. Sodium persulf ate and hydrogen
peroxide/sulfuric acid are non-chelate mild etchants which can be used to .
replace the chelate etchant, ammonium persutfate.
The use of non-chromium etchants such as ferric chloride or ammonium
oersultate will result in a less toxic waste.
'
24
WASTE MINIMIZATION IN THE MCTAL FINISHING INDUSTRY
-------
Many manufacturers have switched to pattern instead of panel plating. This
change reduces the amount of copper which must be etched away, thereby
reducing waste volume and toxicity. This change is not possible in all
instances, but should be encouraged wherever possible.
Additive plating of boards, instead of the conventional subtractive method,
eliminates the need for etchants. However, current additive techniques
necessitate the use of solvent processable resists and the spent baths
contain heavily complexed copper which may Complicate wastewater
treatment. .-.' ;
RECYCLING AND RESOURCE RECOVERY IN
CLEANING AND STRIPPING
Notwithstanding a significant effort in source reduction, most metal finishers
will continue to generate waste. Many options exist for recovering valuable
metals from these wastes. Any type of treatment process beyond simple
neutralization or pH adjustment requires a treatment, storage or disposal
(TSD) permit either under RCRA or California law. treatment activities not
requiring a RCRA permit may be eligible for inclusion in California's permit
by rule program which might be.exempt from permitting requirements.
However a permit by rule still involves agency and public-notifications and
- financial assurance. The generator must check the recycling laws to ensure
compliance before considering onsite or offsite recycling. The requirements
for such an exemption are very specific and the determination is made on a
case by case basis.
SOLVENT RECYCLING
If solvent use is unavoidable, the best waste management strategy to
suggest is recycling with onsite distillation equipment. This equipment can
handle volumes as low as five'.gallons. If the plant operator does not want to
purchase or lease onsite equipment, then offsite recycling should be the
option of the last resort. Care must be taken to avoid cross contamination of
solvents. Mixed solvents are difficult and, at times, impossible to recycle, .
and must be incinerated. - '
AQUEOUS-BASED CLEANFR RECYCLING
- The prospect of recycling aqueous-based cleaners is enhanced through the
use of non-emulsifying cleaners, which limit the separation of oil.
Closed-loop systems have been demonstrated for acid pickle wastes. Spent
pickle liquor has recently been processed through a bipolar membrane,
which results in a regenerated pickle liquor and a filtrate containing the
precipitated metals. ' . - ' ,
Check the
regulation
Still Bottom*
WASTE MINIMIZATION OPTIONS rOR THE METAL FINISHING INbUSTRY
25
-------
liiillillilllllllliiilill
RECYCLING AND RESOURCE RECOVERY IN
SURFACE PLATING AND RELATED PROCESSES
MATERIAL RECOVERY AND REUSE
As regulatory requirements for plating wastes have increased, previously
uneconomical recovery methods have become feasible, particularly for larger
facilities. While smaller facilities may not be able to implement these ,
technologies onsite, they should be informed of their relative merits so thai: they
may make appropriate decisions regarding offsite treatment.
The technologies available are: 1) evaporation, 2) reverse osmosis, 3) ion
exchange, 4) electrolytic recovery, and 5) electrodialysis.
Evaporation
Evaporation is used to reduce the volume of a wastestream for subsequent
treatment or to concentrate a contaminant sufficiently for use as a feedstock.
Atmospheric evaporation systems cannot recover the vaporized water like
vacuum evaporation systems do, but are considerably less expensive- The
energy demand of evaporation systems is their biggest drawback. See
Figure 4.
Reverse Osmosis
Reverse osmosis (RO) technology has long been used to recover plating
chemicals from rinsewater as well as to purify mixed wastewater for reuse. It is
used most commonly to purify rinse water from acid nickel process baths. The
water is returned to the rinse tank while the nickel salts are used to replenish the
plating tank. The method involves forcing metal laden water through a
semipermeable membrane under pressures of 200-to 1200 psi. The membrane
Surface
Evaporation
. ra
Drag-Out
Plating
Bath
i
f
m m
*
"T""-"*-N
' 1
t -
'
f m
<
1
-"" ']
k
3-Stag« Countereuirent Riming
Used Rin«« Wat«r
Concentrate
-Makeup
Water
Condenaate
EVAPORATION SYSTEM
"*'**
Figure*"^
26
WASTr. MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
3-Stag* Counwrcunvnt Rinsing
Slowdown lo
Wast* Treatment
REVERSE OSMOSIS SYSTEM '
" Figure 5
is impermeable to most dissolved solids. The operator must carefully
evaluate the type of membrane and module design to ensure that the unit
will perform adequately and will fit into the allotted space. This method is not
suitable for compounds having a high oxidation potential (e.g., chromic acid)
and must be augmented with activated carbon treatment if non-ionized
organics are present. The. energy costs can be high because of the high
pressures required: See Figure 5.
Ion exchange
Ion exchange is also effective for recovery of drag-
out from rinse waters. The process exchanges ions
of harmless substances contained within the
exchange resin for the ionized metals in the rinse
water. The solid ion exchange particles in the resins
are either naturally occurring inorganic zeolites or.
the more commonly used synthetically produced
organic resins. This system is suitable for chromic
acid rinses and is being usedto recover several
metals (e.g. Ni, Cu, Ag) as. concentrated solutions to
be returned to the process. However, rinse waters
must be segregated to do this. This method is
generally less delicate than reverse osmosis. It can
also be effective in removing/recovering aluminum,
arsenic, cadmium, copper, and cyanide. On the
other hand, ion exchange units require close-.
monitoring and may add to the wastewater x ,
treatment load due to large volumes of regenerant
and wash solutions. "
See Figure 6.
Influent Water. B+ Ions
Ion Exchange
Active Zone
' Treated Water, A+ Ions
Legend: -
B = B+ Ions
<3S>:= Resin Containing B+ ions
©= Resin Containing A+ Ions
A = A+ Ions . '
, Figure 6
27
-------
Electrolytic Recovery
Electrolytic recovery captures metals in solution by plating them out on a thin
starter sheet made of the metal to be recovered or a stainless steel blank, which
serves as a cathode in the tank. The product of this process is a solid metallic
slab, which can be reclaimed or used as an anode in an electroplating tank.
The technology, also called electrowinning, is applicable to rinse water and
spent process baths. This technique requires rinse water segregation to
prevent contamination of the anode with mixed metals.
Electrodialysis
Electrodialysis uses selective membranes to separate anions and cations from
rinse waters. Each component can then be cycled back into the appropriate
tank. See Figure 7.
KTMSF WATER REUSE
Consider the potential of using rinse water following acid cleaning as makeup
water for rinse tanks following alkaline cleaning. The method should prolong .the
life of the rinse water and will enhance rinsing of the alkaline-cleaned workpiece
by reducing the viscosity of the drag-out film. Workpiece quality specifications
will determine whether this method of recycling will work since it results in salt
deposition (ie. spotting) on the part.
Final or critical rinse water may be clean enough for use as makeup water in
rinses requiring lesser effici&ncy. {See discussion of rinse systems in source
reduction section.)
RECYCLING AND RESOURCE RECOVERY IN
PRINTED CIRCUIT BOARD MANUFACTURING
There are several opportunities for recovering metals from solutions involved v
with printed circuit board manufacturing in addition to the methods previously
described for electroplating. ,
Copper from etching baths may be recovered and purified and used as makeup
for the electroplating baths.
. Cupric chloride etchant, reduced to cuprous chloride by the etched copper, may
be regenerated through direct chtorination. This is a new idea and the
equipment arid technology are not currently available.
Recovery of metallic forms of copper, lead, and tin has been demonstrated by
passing wastes through an exchange reactor containing aluminum, which
displaces the metals due to the higher oxidation potential of aluminum.
28
WASTF. MINIMI7AT10N IN THE METAL FINISHING INDUSTRY
-------
Purified Stream
(to rinse tanks)
Concentrated
Steam
(to plating bath)
Anode
Contaminated
Rinse Water
Legend:
M+ = Cations
X- = Anions
IXXXX1 Cation-selective membrane
K\\\j Anion-selective membrane
ELECTRODIALYSIS
Figure 7
WASTE MINIMIZATION OPTIONS FOR THE METAL FINISHING INDUSTRY
-------
30
WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
Review Questions
The Metal Finishing Industry
1. Is there such a thing as a "typical" metal-finishing shop? Briefly
discuss the range of metal-finishing shops. .
2. Why is it important .for the metal-finishing industry to reduce its
waste streams? .
Physical and Chemical Processes
3. What are the primary metal cleaning processes? What are the
advantages and disadvantages for each process?
4. Describe the following chemical and electrochemical processes: ,
' Phosphating, chromating, anodizing, passivation and metal coloring.
5. What occurs during electroplating and electropolishing? How do they
differ? . . ' ' . '
6.. How are metallic coatings placed on workpieces?
7. Describe case hardening^
8. List the steps in printed circuit board manufacturing.
SourceReduction
9. What is the hierarchy in cleaning and stripping? What is the basis for
this hierarchy? -.-/'.
10. What alternatives can be implemented to reduce the need for cleaning?
11. Discuss substitutes for the following-
Solvent cleaners ',-.'. : ,
Alkaline/acid cleaners ; .
Detergents .''.".'.
12. Name the substitutes for both chromic acid brightener and cyanide,
cleaner ; /- ~ '
13. How can material purchasing, handling and.storage contribute to
.source reduction? ', . \ ;
14. What are some of the best ways to avoid or reduce spills?
v ; ."'"'.._ . . i ., .
15. Discuss how frequent and regular inspections by facility personnel can
minimize waste.
REVIEW QUESTIONS
31
-------
16. Review the following techniques for process bath source reduction:
material substitution
extending solution life
drag-out reduction
modified rinse systems
improved housekeeping
17. Name three source reduction techniques for the printed circuit board
manufacturer. .
Recycling and Resource Recovery
18. Discuss solvent and aqueous-based cleaner recycling.
19. Describe how the following technologies are utilized for material recovery
and reuse: :
evaporation
reverse osmosis ' '
ion exchange
electrolytic recovery
electrodialysis
rinse water reuse
32 ' WASTC MINIMIZATION IN THE METAL WISHING INDUSTRY
-------
REFERENCES
Campbell, Monica E. and William M. Glenn. Profit from Pollution Prevention:
A Guide to Industrial Waste Reduction & Recycling. Toronto, Ontario,
Canada: Pollution Probe Foundation.
Guides to Pollution Prevention: The Printed Circuit Board Manufacturing
Industry. U. S. Environmental Protection Agency (EPA/625/7-90/007),
June,, 1990.
Guidelines for Waste Reduction and Recycling: Metal Finishing.
Electroplating, and Printed Circuit Board Manufacturing. Oregon
Department of Environmental Quality, hazardous Waste Reduction
Program, March, 1989.
Hazardous Waste Fact Sheet for Minnesota Generators: Metal
Manufacturing and Finishing. Minnesota Pollution Control Agency and
Hennepin County Department of Environment and Energy, undated.
Hazardous Waste Minimization Manual for Small Quantity Generators.
University of Pittsburgh, Center for Hazardous Materials Research, 1989,
Hazardous Waste Reduction Checklist & Assessment Manual for the Metal
Finishing Industry. California Department of Health Services, TSCP/ATD,
undated.
. Hunt, Gary E. "Waste Reduction in the Metal Finishing Industry". JAPCA. 38:
672-680,1988, \
Mehta, Suresh and Thomas Besore. Alternatives to Organic Solvents in
Metal-Cleaning Operations. Illinois Hazardous Waste Research &
Information'Center, July, 1989. '
Metal Plating Industry Waste Reduction Audits. HMS' Environmental Inc. for
Washington State Department of Ecology, Office of Waste Reduction,
. June, 1989. ,..' ' . ' / ' , :
Nunno, Thomas, Stephen Palmer, Mark Arienti, and Marc Breton. Waste
Minimization in the Printed Circuit Board Industry^ Case Studies. U. S.
Environmental Protection Agency (EPA/600/S2-88/008), March, 1988.
Pollution Prevention Tips: Drag-Out Management for Electroplaters. North
Carolina Department of Natural Resources & Community Development,
1985. . , : ;''-""'" ,/
Pollution PrevehtionTips: Counter-Current Rinsing. North Carolina
Department of Natural Resources & Community Development^ 1985.
Pollution Prevention Tibs: Rinse Tank Design. North Carolina Department
of Natural Resources & Community Development, 1985.
Pollution Prevention Tips: Rinse Water fleuse. North Carolina Department
of Natural Resources & Community Development, 1985.
Reducing California's Metal-Bearing Waste Streams. Jacobs Engineering
Qroup for California Department of Health Services; TSCD/ATS, August,
1989. . . . ' "x. ' .,
REFERENCES ... / .., * , . . . .. .. 33
-------
.- . . : : ,.
Reducing Hazardous Waste Generation with Examples from the Electroplating.
industry. North Carolina State University, School of Engineering, Industrial
Extension Service, 1985.
Rpdnrinn WaW Pollution ffrntml Costs in the Electroplating Industry. U.S.
EnvironrnentalI Protection Agency (EPA/625/5-85/016), September. 1985.
Thibautt James "The Costs and Benefits of Source Reduction in Metal
pniehiAg- in Moptinn Ha7ardous Waste Requirements for MftTal Finishers
(Seminar Publication). U. S. Environmental Protection Agency (EPA/625/4r
87/018), September, 1987;
wast* Anriit Studv Metal Finishing Industry. PRC Environmental _
Management, Inc. for California Department of Health Services, TSCD/ATS
and U. S. Environmental Protection Agency, May, 1988.
waste Audit Study p"nted Cirrilit Roard Manufacturers. Planning Research
Corporation for California Department of Health Services, TSCD/ATS, June,
1987.
waste Minimization in M^i Parts Cleaning . U. S. Environmental Protection
Agency (EPA/530-SW-89-049), 1989.
nirnirflti"" Audit Rsport: Ca*G Studies of Minimization of Cyanide
frnm HentnP18*'"" Operations. U. S. Environmental Protection
Agency (EPA/600/S2-87/056), January, 1988.
34
W/4STE MMIM17.ATION IN THE METAL F/N/SH/NG INDUSTRY
-------
GLOSSARY
Abrasive Blasting
A method used to remove brittle material such as millscale oxide, remains
of paint, etc. More generally referred to as grit blasting. '.'.
Acid Descaling >
An alternative name for "pickling," a process using acid to dissolve oxide
and. scale. . \
Activation
Process of removing last trace of oxide on a metal surface and a thin
layer of the metalitself to ensure that the metal surface to be plated is
eiectrochemically active, (see^etching")
Alkaline Descaling .
A chemical process for removing scale. A typical descaling solution uses
caustic soda with additives such as detergents and chelating agents.
Alloying .
The addition of one metal to. another metal or non-,metal or combinations
of. metals. For instance, steej is an alloy of iron and carbon. Other metals
are added to steels to impart specific Characteristics like strength or
corrosion resistance. .
"Alochrom" ."".",
A proprietary process applied to aluminum and its alloys to improve
corrosion resistance or to prepare surfaces for painting. Treatment
produces an adherent aluminum oxide with some.absorfaed chromate.
Amalgamating
Process in which alloys are formed with mercury such as gold, silver, iron,
copper and aluminum. Due to the toxicity of mercury, use of the
technique is declining.
Annealing
A heat treatment process which may be applied to all metals to soften
them. :.-...-.
Anodic Etching
A form of electrolytic etching where the workpiece being etched is anodic
in the electrolytic circuit (in electroplating, the workpiece is the cathode).
Anodizing
A process generally applied to aluminum and its alloys to produce an
adherent oxide film to impart corrosion resistance or surface hardness.
GLOSSARY ' . . ' .':"'. ' ' - ' " ., 35
-------
Aquablast
A surface cleaning process which can be applied to any material where an ^
abrasive material is suspended in water. The resulting slurry is pressurized t ;
and ejected through a nozzle. Since higher pressures can be used in this
process than in other types of blasting, surface metal can be quickly removed
and leaving a good surface finish.
Blasting
See' listing by specific medium (e.g. Abrasive, Dry, Grit, Shot, Aqua).
Borax Treatment
A method of coating steel with a thin film of dry lubricant. .After surface
cleaning or acid pickling,' the material is placed in a hot borax solution,
allowed to come to solution temperature and removed and dried. The
resulting alkaline coating imparts lubrication for subsequent drawing
operations and provides minor corrosion protection.
Boriding
A high temperature process used for surface hardening of mild low carbon
steels. . "-.
Bright Chrome Plating
Decorative chromium plate deposited directly on a nickel plate substrate.
Bronzing
A chemical process generally applied to steel to impart the appearance of
bronze (antimony chloride in hydrochloric acid followed by ammonium
chloride in dilute acetic acid). The resulting "bronze" film does not have the
corrosion resistance of a true bronze.
Buffing . :
A specific type of mechanical polishing using a high speed disc made from
layers of cloth, leather or plastic impregnated with an abrasive. The
workpiece to buffed is pressed against the disc.
Burnishing . .
A form of metal finishing where the surface is treated mechanically so that no
appreciable metal is removed but the surface is smoothed.
Carbonitriding
A surface hardening technique for steel in which a hydrocarbon (e.g.
propane butane) and ammonia are are injected into a furnace (750 -800 o)
containing the workpiece. The resulting atomic carbon and nitrogen react
with the surface-iron to form iron carbides and iron nitrides.
Carburizing .
A process used for certain types of ductile steel which increases surface
hardness from two to six-limes. It generally is conducted in a heat resistant
box containing an atmosphere of carbon monoxide, carbon dioxide,water
vapor methane, hydrogen, and butane in correct ratios and heated to 900 C.
w/isrr MINIMIZATION ;NTHCMCT*LF/N/SH/NC INDUSTRY.
-------
Case Hardening
A family of surface hardening processes generally applied only to steels.
(See specific listings for carbonitriding, carburizing, chromium plating,
cyanide hardening, electroless nickel plating, nitriding.)
Casting . '
A general term covering a production technique where any metal is
heated until it is molten and then poured into 'a mold, allowed to cool and
solidify.. . , , . " .
Cathodic Etching
A technique applied to steel workpieces where the workpiece is made the
cathode in an.electrolytic cell with sulfuric acid as the electrolyte. The
anode will generally be lead or stainless steel. When a current is applied,
hydrogen will be evolved at the cathode and the surface metal oxide will
be reduced. The technique is usually applied immediately prior to -
electroplating. ,
Cathodic Protection
A technique applied to steel where metals anodic to iron (eig. zinc,
aluminum, magnesium) are applied to the surface on the steel workpiece
to provide a corrosion resistant surface. The process relies on the fact
that where a cell exists between two metals with an electrolyte, one of the
metals will corrode and in the process of corroding protect the other
metal. , ;
Chemical Polishing
A process carried out on mild- and low-alloy,steel,,stainless steel,
aluminum. Special solutions are used to attack the surfaces of these
metals in such a manner that the peaks or corners are affected in
preference to the concave surfaces. The result is a general smoothing of
the surface.
Chrqmate Coating (Chromating)
A corrosion protection technique which has many variations and can be
applied to steel, aluminum, magnesium, and zinc. It results in the
formation of metal oxides on the surface of the workpiece which reacts to
form metallic chromates. Chromating of aluminum and magnesium
improves corrosion'resistance considerably. With steel it is much less
permanent.- . , , ,
Chromium Plating
This electrodeposition of chromium is generally applied to steel in all its
forms. It is usually done for decorative purposes (bright chromium) or to
provide a hard surface for engineering purposes (hard chromium).
Chromium plate is nearly always deposited on top of a nickel deposit.'
The nickel deposit supplies the necessary eorrosion resistance. '. -
\ ' , ' : ' . "'\. ' - ' '
Chromium plating solutions contain chromic acid (500 gm/l) and sulfuric
acid(5gm/l). Proprietary additives are sometimes used to improve
throwing power, regulate the solution and to help the distribution of
current. .
.GLOSSARY* .' . '".-'.- -''-..' ' . , , -"' 37
-------
miiiilliiillllllilillii , . / ,. . ,
Chromizing
A treatment applied to mild- and low-alloy steel only. It is a surface diffusion
process in which chromium is alloyed with iron to give a chromium-rich
surface layer.
Thoroughly cleaned workpieces are'placed in a heat resistant box with a
proprietary powder of an unstable chromium compound. When the box is
heated to over 1000° C, the chromium decomposes into an active state which
reacts with the iron to produce an alloy. The longer the workpiece is retained
in the heated box the deeper the penetration the chromium alloy.
Cold Galvanizing
A term sometimes used to differentiate between electroplating zinc on steel
from the hot dipping of steel in molten zinc. It can also refer to a form of
painting with specialized paints which result in a film of up to 90% powdered
zinc. The purpose of all these processes is to provide corrosion resistance.
Color Anodizing
A process used only on aluminum and its alloys using dyes to color the
anodic film. The anodic process produces a porous film which when fresh
will absorb dyes. The anodizing is carried out using the sulfuric acid process.
After completion of the anodizing the workpieces are rinsed in cold water and
placed in a dye solution. After dyeing, the workpieces are again rinsed in
cold water followed by immersion in nearly boiling water. The heat seals the
anodic film and the surface remains permanently colored.
Contact Tin Plating
A form of electroless plating commonly used in thfe printed circuit board and
general electronics industries to improve solderability of workpieces. The
workpieces are immersed in a hot chemical solution containing unstable tin -
compounds. The tin reduces on the surface of the workpieces.
Copper Plating
Copper is electrodeposited for conductivity in the printed circuit and electrical
industries, and for decorative purposes. There are four basic types of copper
plating solutions; copper sulfate, copper cyanide, copper pyrophosphate, and
copper fluoborate.
The oldest technique uses copper sulfate (200 gm/l), sulfuric acid (30 gm/l)
and potassium (12 gm/l). Modern solutions use proprietary additives which
make it possible to plate at higher temperatures and with a high "leveling"
action. .
Copper cyanide solutions are often used when steel is to be plated. It
- produces a thick, dense,, non-porous film. A typical copper cyanide solution
consists of copper (8 gm/l), and free sodium cyanide (5 gm/l).
Like cyanide, copper pyrophosphate solutions can be used for plating on
steel provided an initial "strike" is made before plating. The "strike" solution
will usually contain copper (5 gm/l), pyrophosphate (60 gm/l), oxalate (5 gm/l)
and chloride (10 gm/l). "It-may be heated up to 50° C. After the "strike" the
workpieces are placed in tn& standard pyrophosphate plating solution which
contains copper (20 gm/l), pyrophosphate (160 gm/l), oxalate (17 gm/l) and
ammonia (6 gm/l). The pH ofthe bath must be maintained at 8.4. Additives
are generally present to give good "leveling". Pyrophosphate solutions
38 ' WASTE MINIMIZATION fN THE MFML FINISHING INDUSTRY
-------
require careful control and are more expensive than some alternatives,
but give a bright, dense deposft with good throwing power.
Copper fluoborate solutions are used when a rapid build up of thick
deposits is necessary. Tight laboratory control is generally required for
optimum plating efficiency. A typical solution contains copper (120 gm/l),
fluoboric acid (30 gm/l), and is operated at 45° C.
Corrosion
Corrosion occurs in all metals at some time and can be divided into four
basic forms. Room temperature oxidation, by far the most common form,
is most obvious in mild and Ipw-ailoy steels. The process is accelerated
dramatically by comparatively small amounts of contaminants like
chloride, sulfate, and fluoride. ,
When exposed to high temperatures, metals will almost invariably result in
oxidation of metal surfaces. Chemical corrosion is the result of attack by
acids or alkaline compounds which dissolve the metal surface.
Electrolytic corrosion occurs when two metals in contact with each other
have different' electrode potentials. It 'is a major contributor to most of the
corrosion found in steels.
Cromodizing
A name given to the chromating of steel where a film of iron chrpmate is
formed on the surface. 'The corrosion protection provided by this
treatment is of a very low order. "Phosphating" and oiling will probably
provide superior corrosion resistance without the use of chromium.
Cyanide Hardening
A surface hardening technique which uses molten cyanide salts to give
, workpieces a case containing carbon and nitrogen. Temperatures of
650° C to 80° C must be maintained for 20-30 minutes to 6e effective.
The high toxicity of the cyanide used makes it expensive because of
treatment requirements. ' ,
' ' " -
Degreasing
A form of cleaning which generally uses chlorinated solvents. In the most
common form, a liquid solvent is heated in an open topped container. As it
boils a hot vapor rises above the .liquid. The vapor js held within the
container by means of a cooling coil which runs around the inside, of the
container a short distance below the rim. This cold zone causes the
. vapor to condense and be returned to the sumpfor rebelling. It is
therefore a form of continuous distillation.
When any cold component is placed in the container, the vapor
immediately condenses on the surface. The solvent dissolves any grease
on the surface arid as further solvent condenses it runs off the workpiece
carrying the soluble soils into,the sump.
Descaling . X
This term describes a process that can be applied to all materials to
remove scale.' Scale is generally produced during manufacture or storage
GLOSSARY ' . ' " , - 39
-------
and it may be obvious such as rust or millscale or it may be very unobtrusive.
The various methods of descaling include blasting, pickling, acid or alkaline
sodium hydride treatment, and polishing.
Die-casting
A method of casting in which molten metal is poured, sometimes under
pressure, into a mold or die. The die is made of metal and immediately after
" solidification of the casting the die opens and the casting is ejected.
Dry Blasting
A general name given to any form of blasting where the abrasive agent is not
carried in water.
Dry-form Lubrication
A form of painting applied to steel surfaces of workpieces subject to light
wear or abrasion. It generally uses colloidal graphite or molybdenum
disulfide carried in a phenolic resin.
Electrocleaning > '
An electrochemical cleaning process by which a workpiece is first made the
cathode in an electrolytic cell. When current is applied, the generation of
hydrogen gas from the electrolysis of water at the surface of the workpiece
results in a highly efficient scrubbing action. Following initial treatment as a
cathode the circuit is reversed so that the workpiece is the anode. Oxygen
gas, which is generated at the surface produces a final cleaning action.
Electroforming
A specific form of electroplating used where intricate shapes and relatively
thin metal deposits are required. .Molds of plastic, wax. or sometimes metals
are made conductive by application of carbon or metallic powder and are
plated by conventional methods. Nickel, copper or precious metals are
generally selected for plating. The mold is generally removed at the
completion of the plating process by one of a number of methods depending
on the material from which the mold is constructed.
Electrogalvanizing
See "Zinc Plating"
Electroless Plating
When a metal is immersed in a solution of another metal with a higher
electrode potential, that dissolved metal will displace the lower potential metal
on the surface of a workpiece. The best known electroless plating process
occurs when steel is placed in a copper sulfate solution. Copper is plated
without the application an external electric current.
In another common electroless process, aluminum, which rapidly forms
aluminum oxide in conventional electrolysis, is plated with zinc. The zinc
deposit can then be subsequently electroplated using conventional
techniques.
'
WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY .
-------
Electroless Nickel Plating
In this process an alloy of nickel and phosphorous can be applied to
almost any metal, and to many plastic materials including- glass. Prior to
nickel deposition, the workpieces must be cleaned to a very high standard
and then "etched" or "sensitized" before they are immersed in the
electroless nickel plating solution. The solutions must be heated above
80 C for good adhesion to be achieved^ ,
Electroless nickel plating has found considerable" use in two major
applications. First it is employed where good corrosion resistance is
required on intricate shapes, crevices, blind holes and deep cavities
where conventional electroplating is not possible. Electroless nickel
deposits occur in homogeneous, uniform manner on all surfaces as
opposed to in electrolytic plating where there will always be areas of high
current density, such as edges and points where deposits are thicker, and
areas of low current density, such as recesses, where deposits are
thinner. . .
'"'."!' - ' -~ . " - ' - '
The second major area of use is where, after electroless plating, heat
treatment is employed to obtain a high surface hardness.
Electrolytic Etch
A technique generally applied to steels which attacks the surface to
produce a clean, oxide free material. It is often used prior to
electroplating, especially chromium plating. Since it preferentially attacks
edges it will open up minute cracks in the metal surface allowing
Electrolytic etching to be used as an inspection technique. ,
Electrolytic Polishing
An electrochemical process usually applied to steels and aluminum and
its alloys which produces a bright surface with a highly reflective finish. In
most instances this is used for decorative purposes and it often
associated with some other form of metat finishing such as anodizing,
plating, or lacquering.
In electropolishing the workpiece is made the anode in an electrolytic cell.
When current is applied metal is removed from the anode surface.
Corners and peaks are preferentially dissolved because of the higher
current density surrounding them. The result is the surface of the
workpiece is smoothed.
The electrolytes employed generally are sulfuric acid, phosphoric acid or
chromic acid. Alternatives methods of polishing include "barreling" or
other forms of mechanical polishing, and vapor blasting..
Electro-osmosis
See "Reverse Osmosis"
Electrostatic Painting
, A form of spray painting using specially.formulated paints with pigment
particles which will accept a static electric charge and be carried in a non-
polar solvent. Paint guns eject the paint at a slight velocity. The particles
. . I - ' : ' ..." / / 41
. GLOSSARY ' ; ' .--'''' ; ' . ' . ,...,'
-------
leaving the gun are given an electrostatic charge of anything up to 30,000'
votts. Very small currents are employed so the safety hazard is negligible.
The workpiece to be painted is at earth ground and thus ther6 is considerable
attraction between the paint and the workpiece. As the paint particles arrive
at the workpiece, they are attracted and adhere to the surface. This results in
the neutralization of the static charge, and added attraction of the paint
particles to areas which have not been painted.
Emulsion Cleaning
A cleaning technique which acts by emulsifying contaminants. Emulsions are
mixtures of two liquids, with one liquid holding the other one in a suspension
similar to a colloidal suspension. The liquids will typically have different
polarities and will dissolve different types of materials. One of the liquids is
usually water and the other will have non-polar properties. They can
therefore be used to dissolve non-polar contaminants like oil and grease from'
metal surfaces.
With proper use emulsion cleaners can have a long useful life and produce
very clean surfaces. They may have to be formulated specifically to clean
certain soils.
Etching
Etching may be used as a surface preparation technique prior to
electroplating (see "Activation") or for removal of metal such as in the printed
circuit industry where material not required on the finished product on the
final printed circuit is removed by a chemical solution.
It can also be used as an inspection technique due to its ability to accentuate
surface cracks and defects. Even minute surface defects will be highlighted
since the edges are preferentially dissolved..
Evaporation Process
See "Vacuum Deposition"
"Ferrostan" Process
' A method of continuous electrolytic tin plating of steel strip in which cold
reduced strip is continuously fed through the cleaning, etching, plating and
rinsing processes. The solution is generally an acid sulfate which produces a
matt finish.
Fire Gilt Process
A process confined to the jewelry trade in which gold dissolved in mercury
(gold amalgam) is wiped on surfaces to be plated. When the article is heated
the mercury is driven off leaving a gold film. The process represents a
considerable health hazard due to the emission of the mercury vapor.
Fluxing
A process used in the heating of metals which may be intended to reduce or
eliminate oxidation, confine the products of oxidation, reduce their melting
point, and improve fluidityof surface metal layers. Fluxing is generally used
in casting, welding and soldering.
42 WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
Frosting
A type of metal finishing where a fine matt finish is produced by using
techniques such as acid-etching, blasting, scratch brushing or barreling. .
Galvanic Protection
A general term used in the corrosion protection of steel. Technically, it
, refers to a metal used to protect a metal higher than itself in electrode
potential. In practice, it refers to the use of zinc to protect steel.
i > ' . . .
Galvanizing
A corrosion protection technique applied only to mild steel, cast iron, and
steel alloys in which workplaces are immersed in liquid zinc at 500° C. A
zinc/iron alloy is formed at the surface of the workpiece giving it an
adherent coating of zinc. .
Prior to galvanizing, the metal surface must be in a moderate state of
cleanliness. This is generally accomplished by light acid pickling or
blasting. - . .
Galvanized coatings are generally about 0.005 inches thick and can give
a protection for 10 to 20 years. . . »_.
Gilding
A process in which gold is coated on the surface of another base metal.
Gold leaf, a layer beaten or, rolled so thin it is porous to light, is glued or
beaten onto the article to be gilded. A similar method applies a fine gold
powder mixed with a flammable liquid solvent applied to the article like a
paint. The solvent is allowed to evaporate or in some cases may be
ignited.
Gold Electroplating '
. Gold has two specific properties which make it valuable in industrial and
commercial uses, it resists oxidation and corrosion to a very high degree
and it retains its attractive color. ,
In industry, gold is now finding considerable use in the electronics field.
While gold has a conductivity of only 60% that of copper, it has the
advantage that it.will retain that conductivity over a wide variety of
conditions. . ' '
Traditionally, gold has been plated from high concentration cyanide
solutions which are often produced by immersing the gold in the cyanide
dissolving the metal as gold cyanide. The solution may then be used as
the electrolyte with an inert anode. .."'-.
The main advantage of gold plating over other methods of applying gold
to surfaces, is that electroplated coatings do not have pores as gilded
coatings do. this provides significantly greater life and corrosion
resistance.
Grit Blasting
A technique of abrasive cleaning or surface preparation using sharp
particles (e.g. cast iron shot, aluminum oxide). It covers such processes
'." -'' ' - " , . : '.'':. ' ''-.'" -43>
GLOSSARY , . '-'.
-------
IIIIIIIIHIIlllllIllllli . M^rffni,,
as removal of scale, corrosion, paint and other surface, films. Use or,tree
silica presents a health threat and should be avoided.
Hard Chrome Plating
See "Chromium Plating"
Hard Facing
A term referring to processes used to harden metal surfaces and impart wear
resistance by a variety of heat treatments. Also see "Metal Spraying"
Hot-dip Coating
See "Galvanizing"
Hydrogen Embrittlement
A defect which occurs during the electroplating process. Atomic hydrogen is
produced at the cathode of the workpiece being plated. This atomic
hydrogen" is extremely reactive arid has the capability of entering the
interstices of the metal. Being unstable in the atomic state, the hydrogen will
combine as rapidly as possible with other atoms to form molecular hydrogen.
This molecular hydrogen, having a higher unit volume than atomic hydrogen,
results in internal pressure in the plated metal.
Immersion Plating
A plating technique similar to electroless plating where a more electropositive
metal dissolved in an electrolyte is plated onto the surface of a less
electronegative metal workpiece. The term immersion plating is used where
a deposit is obtained and the plating process then stops. This is
distinguished from electroless plating where the deposition of the metal being
plated continues to be deposited as long as the workpiece remains in the
solution.
Inchrom Process
See "Chromizing"
Indium Plating ....
Indium is a metal not unlike lead but with friction, and corrosion resistant
properties which are unique. In fact, the sole purpose of indium plating is
improving the friction characteristics of very high-rated bearing.
"Kanigen Plating"
Rrst proprietary process for electroless nickel plating. For more information
see "Electroless Nickel Plating"
Lacquering .
A term which refers to applying a clear non-porous varnish, to protect an
existing finish. Most lacquers are cellulose-based nhatenals in which
cellulose is dissolved in a solvent. They are generally applied by 'spray or
brush. The solvent is allowed to evaporate leaving a thin film of cellulose
remains on the metal surface.
. WAST£ MINIMIZATION IN THE METAL WISHING INDUSTRY
-------
Lead Plating
Lead plating does not have many common uses except in the production
of electrodes for lead acid batteries. Steel, which has been plated with
lead is much stronger mechanically and lighter than the same thickness of
pure lead. It is also used as a base layer for indium plating. Lead plating
solutions contain approximately 100 gm/i lead and 40 gm/l fluoboric acid.
Leveling \
EIe<:trodeposited metals tend to be concentrated at sharp corners, peaks
and ridges, due to the fact that current distributed on a surface will tend to
concentrate at these irregularities much more than in concave surfaces
such as recesses. Therefore, when a workplace with a rough surface is
electroplated, the rate of deposition will be faster on these the convex
irregularities. The result will be accentuation of the item's original '' <
roughness.
To counteract this effect, additives are added to the electrolyte solution
which produce a polarization effect which is concentrated at the peaks
and ridges. This polarization effect lowers the current density at me
peaks and thereby reduces the rate of deposition. The net result is to
smooth or "level" the metal surface.
Metal Coloring
Dyes applied after anodizing or plating to color-code (ie. identify) parts.
Metal Spraying
The general term is applied to the spraying of one of several metals onto ,
a metal substrate. In general, ft is intended to produce three effects. The
first, cprrosion protection, usually involves spraying zinc or aluminum on
structural steel components. It is also used on high tensile workplaces
such as those used in aircraft, which cannot be electroplated due to
hydrogen embrittlement. ......
The second purpose for metal spraying is "hard facing". Materials used in
hard facing are tungsten bearing or tungsten carbide materials, cobalt and
nickel with small amounts of chromium, and high manganese chrome
materials. These materials provide significant resistance to wear.
The third application for metal spraying is for salvage purposes. When
engineering components are found to exhibit wear while in service,
technical and economic considerations may make metal spraying to
replace the wear a better alternative to replacement.
The most common method of metal spraying is "flame impingement". The
technique uses powdered metal continuously fed into a high velocity
flame. The flame atomizes the metal powder into a molten state and the
particles are then projected by the energy of the flame onto a prepared
metal surface.
Plasma coating is a similar method which employees radio frequency-
induced plasmas at temperatures up to 30V000° C. This method is limited
to high integrity components where excellent adhesion or sophisticated
materials are required.
GLOSSABX
-------
MIIIIHIIIIIIIIillllli , -
"Micro-Chem''
A proprietary electrocleaning process used for "brightening" and "passivating"
stainless steel. It is a form of electropolishing which gives a considerably
smoother and shinier finish.
Nickel Plating .
A very common form of electrolytic deposition which is generally used as an
, undercoating for subsequent deposits. There are three common solutions
used in nickel electroplating; Watt's solution, sulfamic acid, and electroless
plating. For a complete discussion of the latter, see "Electroless Nickel
Plating".
Watt's solution typically contains nickel sulfate (300 gm/l), nickel chloride
(50 gm/l) and boric' acid (35 gm/l). The mixture of constituents is necessary -
to properly balance the solution. Nickel chloride is required to counteract
nickel sulfate's low conductivity. Without boric acid to act as a buffer, the
plating process would make the solution increasingly more acidic. Baths are
usually maintained at 40d C or above to achieve the best results.
Nickel sulfamate plating is a more recent development. It uses a solution
containing nickel sulfamate (500 gm/l), boric acid (30 gm/l) and nickel
chloride (5 gm/l).
Nickel plating is most often used to prior to deposition of bright chromium
deposits for decorative purposes or where a very hard surface is required. ,
For this reason nickel plating is usually applied in a "bright" condition.
Because of the high cost of nickel it is often applied over a bright copper
deposit. The bright copper deposit does the initial leveling of the surface of
the workpiece so only a relatively thin layer of nickel is required.
it i. '
Nitriding
A surface hardening process which is applied only to certain types of steel
which results in the hardest surface attainable by heat treatment. The
process consists of maintaining workpieces in a 500° C ammonia atmosphere
for up to 100 hours. Under these conditions atomic nitrogen combines with
surface, iron to form iron nitride. The nitrogen slowly diffuses away from the
surface as long as the proper temperature is maintained. The resulting case
thickness is therefore dependent on length of the heat treatment.
Passivation
The cleaning of stainless steel with nitric acid to remove carbon and other
impurities.
Phosphatihg
A process by which the surface of a steel .workpiece is converted to iron
phosphate usually as preparation for painting. Before phosphating, surface
must be free from rust and scale. This is usually accomplished.by acid
pickling or mechanically by wire brushing or blasting.
Phosphating takes a relatively short time, usually five to twenty minutes.
Solutions are usually maintained between 60° C and 90° C. Workpieces are
generally either painted drchromated within 24 hours after treatment since
the corrosion resistance imparted by phosphating is poor.
*C .' WASTE MINIMIZATION IN THE METAL FINISHING INDUSTRY
-------
Pickling
A chemical treatment which removes oxide of scale from the surface of. a
metal. It most often refers to the use of sulfuric or hydrochloric acid to
remove scale formed on mild and low-alloy steel during hot forming
operations. Treatment of stainless steel or high nickel alloys; is done with
hydrofluoric acid, a particularly hazardous material which must be handled
with extreme care.
Reflowing
A technique used in the printed circuit board industry in which a
component is heated in order to melt solder deposits and cause them
flow. It produces a bright attractive looking material, but its main purpose
is for quality control. With reflowing, any defect on the substrate will not
wet, clearly indicating areas\where solder is missing.
Rustproof ing
A general term which refers to processes applied to steel. It may include
painting or galvanizing, but most often refers to phosphating and similar
low duty rust preventatives. ,
Sacrificial Protection - ,
A corrosion protection technique which uses a metal of lower electrode
potential to protect a metal of higher electrode potential. This is possible
because in the'presence of an electrolyte an electrochemical cell is ,'
established in which the lower potential metal acts as a anode and the
metal to be protected acts as a cathode. The anode corrodes and
deposits on the surface of the cathode. In practice, zinc and aluminum
are the two metals most commonly for sacrificial protection
- - *"''- " ' .''' '" '
Sealing ,
A term commonly applied to any metal process having a subsequent
treatment capable of affecting this previous process in order to give
increased corrosion protection (i.e. anodizing^ phosphating).'
Sensitizing
A relatively non-specific term used to cover a range of metal finishing
processes which improve the treatability of a metal surface for a
subsequent process. It often refers specifically to a part of the electroless
plating procedure on plastics or non-metal surfaces. After the surface has
been etched it is reacted with solution which deposits a very thin film of a
metal or metallic compound. The surface is then referred to as sensitized.
Silver Plating; '"
Silver, the easiest metal (for use in plating), is deposited for decorative
. purposes on household and jewelry items. It is sometimes used by the
electrical industry where it is plated over copper to improve corrosion.
resistance. . ,
A typical silver plating solution contains silver cyanide (19 gm/l),
potassium cyanide (15 gm/l) and potassium carbonate (25 gm/l).
' "
GLOSSAKf
-------
ililllllllllllllllllilll! ! ' " . ' . ' ' . ' , , . . """
Solder Plating
The term covers the deposition of an alloy of 60% tin and 40% lead which is
widely used in the electrical and electronics industries. It provides two
valuable features, corrosion resistance and "solderability".
A typical plating solution contains tin (stannous chloride, 55 gm/l), lead
(25 gm/l) and free fiuoboric acid (40-100 gm/l). Organic additives like glue
are often added to the solution to reduce the amount of granular deposits.
Solvent Cleaning
Solvent cleaning normally uses chlorinated hydrocarbons, methylated spirits,
or methyl alcohol. Cleaning with carbon tetrachloride, benzene, toluene,
xylene and ether should not be permitted because of health hazards posed
by these substances.
Workpieces are either wiped with a solvent soaked cloth or dipped in liquid
solvent to remove soluble soils. The soil becomes dissolved evenly
throughout the solvent and on the surface of the workpiece when it is
removed and evaporated. .
Solvent Degreasing
See "Vapor Degreasing"
Stop-off
Method of protecting portions of workpiece surface from chemical processes.
1 Waxes, lacquers or special tapes are applied to areas to prevent chemical
attack or deposition.
Surface Hardening
A general term referring to methods for making the surface of steel
workpieces mechanically harder than their inner portions. .Also see:
"Nitriding", "Garburizing", "Cyanide Hardening", "Carbpnitriding".
Ultrasonic Cleaning
A sophisticated method of cleaning in which adherent soils are removed by
ultrasonic energy applied through liquid. The energy takes the form of cycles
of positive and negative pressure in the surface of the workpiece. With a
liquid acting as a working fluid, the high frequency (up to 10 KHz) pushing
and pulling loosens even tightly adherent soils. It is particularly effective on
surfaces placed directly in the tine beam of energy. It has limited application
Where intricate shapes with many recesses require cleaning.
Vacuum Deposition
A process in which certain pure metals are deposited on a substrate. The
technique relies on the fact that, in a vacuum, pure metals can be vaporized
at a tow temperature in a closed container. The metal vapor will condense
evenly on all surfaces to give a metallic coating. Aluminum is the most
successfully deposited material, producing a highly reflective finish.
c '>. ' :. v
- ' : , -X ' ' : ' -
43 WASTE MINIMIZATION IN THE MZTAL FINISHING INDUSTRY
-------
Vapor Degreasing
A form of cleaning which generally uses chlorinated solvents, which have'
excellent decreasing properties in their own right but also produce vapors
, which are heavier than air. In a typical vapor degreaser, a solvent is
heated in an openrtopped container and as it boils it produces a hot vapor
which rises above the boiling liquid. The vapor is held within the container
by means of cooling coil which runs around the inside of the container a
short distance below the rim. , ..
When a cold workpiece is placed in the vapor zone, the vapor
immediately condenses on the surface, producing a hot clean solvent.
The solvent dissolves any grease on the surface and as more vapor
condenses and runs off, carrying the grease with it into the sump at the
bottom of the sump for re-boiling.
Wetting Agents ;
Chemicals which reduce the surface tension of water, allowing it to flow
from work pieces without beading up.
Zinc Coating
See "Galvanizing"
Zinc Phosphating
A process applied to.freshly zinc plated workpieces which are immersed
in a zinc phosphate solution acidified with phosphoric acid. The zinc
surface deposit is converted to zinc phosphate. The workpieces are then
immersed in a dilute chromic acid solution to seal the zinc phosphate
deposits and prevent formation of unsightly zinc oxide.
Zinc Plating
this very cbmmon form of plating is used to provide corrosion resistance
for steels. There are three widely used types of plating solutions, two of
which employ cyanide. In the first, a high cyanide solution, typically
contains zinc (30 gm/l), sodium cyanide (85 gm/1) and caustic soda
(25 gm/l). .
The second solution is a low cyanide solution. It typically contains zinc
(8 gm/l), sodium cyanide (8 gm/l), and caustic soda (65 gm/l). The third
is an acid zinc solution which typically contains zinc (30 gm/l), sodium
. chloride (25'gm/l), and boric acid (15 gm/l).
Zincate Treatment
A pretreatment necessary for aluminum and its alloys before
electroplating. After cleaning, etching in chromic or phosphoric acid to
remove oxide and dipping in nitric acid to activate the surface, workpieces
are immersed in a sodium zincate solution. Metallic zinc is deposited on
the surface of the workpiece. It is then rinsed and immedfately brought to
the final plating operation. ,
N. '
X
GLOSSAKT
-------
-------
SECTION III
Studies
-------
\
------- |