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INTRODUCTION
This pollution prevention (P2) project was conducted as part
of a joint venture between the U.S. Environmental Protec-
tion Agency (EPA) Region 9; the Arizona Department of En-
vironmental Quality (ADEQ); the City of Phoenix; the Ameri-
can Electroplaters and Surface Finishers Association (AESF);
and Astroplate, Inc. (Astroplate). This partnership was cre-
ated to promote P2, identify P2 technology needs, and accel-
erate P2 technology transfer within the metal finishing in-
dustry. Technical support for the project was provided by
Tetra Tech EM Inc. (Tetra Tech). The project was funded by
EPA Region 9.
BACKGROUND
Spent process baths can be a significant and costly waste stream
for metal finishing facilities to manage. Numerous factors
can cause a bath's performance to degrade, such as depletion
or imbalance of bath chemistries and buildup of contami-
nants from dragin or other sources. When a bath becomes
spent, it is typically batch treated on site, bled into an on-site
wastewater treatment system, or containerized for off-site treat-
ment and disposal. Frequent bath dumps lead to excessive
process chemical use, increased treatment chemical use and
labor requirements, and greater sludge generation.
The life of a process bath can be extended through simple
process control and bath contaminant reduction techniques,
resulting in significant waste reductions and cost savings for
a facility. The case study in
this fact sheet describes tech-
niques that extended the life of
a nickel acetate seal bath at the
Astroplate metal finishing fa-
cility in Phoenix, Arizona.
However, the concepts de-
scribed in this fact sheet are
applicable to a variety of
types of process baths.
Cbst Factors far
Spent Bath Disposal
~ Process chemical
purchases
~ Treatment chemical
purchases
~ Treatment labor
~ Sludge disposal
Bath Life Extension Techniques
A crnbinaticn of these techniques can provide inproved
bath performance and increased bath life:
Reduce dragin contaminatian
• Increase draining time for parts
• Modify rack position for parts
• Add nore rinses or a spray system
Inprove bath purity
• Use deionized (DI) vater for bath makeup
• Filter bath crntinuously
lYbintain bath within control parameters
• lYfeasurepH, tenperature, and ccncentraticn daily
• Add chemicals only when needed
Use a bath additive, or "enhancer"
CASE STUDY: ASTROPLATE, INC.
Astroplate operates a small metal finishing facility that per-
forms sulfuric acid anodizing and chromate conversion (chem-
film) of aluminum parts for aerospace and industrial cus-
tomers. Astroplate has 23 employees, runs two shifts per day,
and uses a manually-operated hoist to move parts on racks
through process steps. Anodizing process operations at the
facility include alkaline cleaning, alkaline etching, acid clean-
ing, deoxidizing, anodizing, dying, and sealing.
.Asazesizlt cffefcfr life etfHTStim techniques, Astrqplate
decreased generation of spent bath solution by 74%.
The resulting annual cast savings is $12,130.
Anodizing is an electrolytic process in which a porous oxide
surface is formed on aluminum parts to provide wear- and
scratch-resistance; corrosion protection; and a decorative tex-
ture, color, and appearance. Sealing, the final process step in
aluminum anodizing operations, improves the corrosion re-
sistance of anodized surfaces by penetrating and closing the
pores of the oxide layer. A good seal is clean and clear,
whereas a poor seal may leave a fine film layer (known as
"smut") or yellow tint on the part. Before sealing, color is
ENTPS-
DECEMBER1997
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often imparted to anodic coatings for decorative or identifi-
cation purposes by impregnating the pores with dyes or min-
eral pigments. Nickel acetate solution is the most commonly
used seal for dyed anodic coatings because of its ability to
retain the color of the dye.
Tetra Tech performed a P2 assessment at the Astroplate facil-
ity in August 1996 and identified spent nickel acetate solu-
tion as a frequently generated and costly waste. Astroplate
operates a single, 560-gallon nickel acetate seal bath. Nickel
acetate sealing follows dye operations (primarily black dye)
and is the final process step on Astroplate's anodizing line.
Astroplate dumps the nickel acetate bath when smut begins
to form on sealed parts. On-site batch treatment records
indicated that the nickel acetate bath was dumped an average
of 2.3 times per month, resulting in about 1,290 gallons of
spent nickel acetate solution being generated each month.
Because spent nickel acetate baths were treated more often
than other process baths, they accounted for a significant
portion of the facility's wastewater treatment costs and sludge
generation. Each month, Astroplate spent about $470 for
process chemicals, $380 for treatment chemicals, $450 (nine
hours) for labor, and $80 (150 pounds) on sludge generated
from treating spent nickel acetate baths (see Figure 1).
Based on an evaluation of facility process operations, Tetra
Tech and Astroplate determined that frequent nickel acetate
bath dumps were the result of (1) inadequate process control,
and (2) dragin from preceding process operations that con-
taminated the bath. Consequently, the strategy for extending
nickel acetate bath life focused on (1) maintaining process
bath control, (2) decreasing bath contamination, and (3) us-
ing a bath additive.
MAINTAINING PROCESS BATH CONTROL
A process bath that is maintained "in control" performs bet-
ter and longer than a bath whose operating parameters are
not maintained within specific ranges. Operating param-
eters that may affect bath performance include (1) concentra-
tion, (2) pH, and (3) temperature. Astroplate uses
Anoseal 1000, which is manufactured by Novamax Technolo-
gies, Inc., of Atlanta, Georgia, as the nickel acetate bath chemi-
cal. At the time of the P2 assessment, Astroplate performed
nickel acetate bath dumps based on visual observation of sealed
parts, did not measure any bath parameters, and did not make
any chemical additions to the bath.
Following the P2 assessment, Astroplate began to monitor
and record the concentration, pH, and temperature of the
nickel acetate bath. Initially Astroplate maintained these pa-
rameters within the chemical manufacturer's recommended
ranges, but the facility eventually determined the best operat-
ing parameters for its own process application. Astroplate
maintained the concentration of the bath at 1.5 to 2.5 per-
cent nickel acetate by making chemical additions as needed.
Astroplate determined that maintaining the concentration
in this range resulted in acceptable seal quality while reduc-
ing nickel acetate chemical use.
Astroplate maintained the bath pH between 5.8 and 6.0 by
lowering the pH with acetic acid and raising it with dilute
ammonium hydroxide. Astroplate also maintained the tem-
perature of the bath at 155 to 165 °F. The facility operated
the bath below the temperature range recommended by the
chemical manufacturer to reduce evaporative water loss and
minimize part heating, which reduces streaking and spotting
on parts as they are transferred to the rinse.
DECREASING BATH CONTAMINATION
At the time of the P2 assessment, Astroplate's nickel acetate
bath was being contaminated by black dye dragin and city
water used for bath makeups and additions. To decrease
bath contamination, Astroplate (1) installed a continuous fil-
tration system on the nickel acetate bath, (2) used DI water to
make up new nickel acetate baths, and (3) modified the rinse
system on the preceding black dye operation to include spray
rinses. Each of these techniques is described below. The tive
Nickel Acetate Seal Process Bath CfcnfctQL
Parameter
Temperature
pH
Concentration
Chemical Manufacturer's
Recommended Range
185 to 190 °F
5.8 to 6.0
3.0 to 4.0%
Astroplate's
Control Range
155 to 165 °F
5.8 to 6.0
1.5 to 2.5%
Measurement
Frequency
Daily
Daily
Every 2 days
Measurement
Method
Meter
Meter
Titration
$1,400
O
>>
Total Monthly
Cost = $1,380
Tofef Nickel Acetate Solution
Treated = 1,290gal/mo
Skr^e Disposal Cost = $80
--
Treatrrert
--
Labor Cost = $450
--
Treatrrert
--
Chemical Cost = $380
--
Nickel Aoetcte Cost = $470
1
Figure 1. Nickel Acetate Bath Monthly Costs
-------
costs of implement-
ing each of these
techniques are in-
cluded in the Costs
section on the last
page of this fact
sheet
Filtration: Filtra-
tion is used to re-
move suspended
solids in the pro-
cess solution that
may gradually
build up and im-
pair the nickel ac-
etate seal, A filtra-
tion system also cir-
culates the process
solution, which
maintains a uni-
form bath tempera-
ture and concentration. Filtration systems are sized accord-
ing to solids loading and flow rate and are available with in-
tank and external configurations. Astroplate installed an ex-
ternal filtration system manufactured by Serfilco, Ltd., on
the nickel acetate bath (see Figure 2), The filtration system
housing holds six cartridge filters, and a centrifugal pump
continuously circulates solution through the system. To pre-
vent pump damage when the cartridges become fully loaded,
Astroplate installed a pressure-sensitive, automatic shutoff
switch on the filtration system. Astroplate uses 20-micron
cartridge filters in the system that are replaced about once
per week, Spent filters are cleaned in an acid strip bath and
disposed of appropriately.
Tj^tallingmaitxirBtic^xtaEEarLttBfiltxatjcn^r'sben
prevents thepwp fromburrdrg outvihen. the filters
beaxve heavily leaded cr clogged.
DI Witter: Originally Astroplate used city water to make up
new nickel acetate baths. However, using DI water for bath
makeups minimizes the introduction of compounds often
found in city water that can decrease bath quality. For ex-
ample, laboratory analysis indicated that tap water in Phoe-
nix had an average concentration of 14 mil-
ligrams per liter of silicate, a compound that
can decrease nickel acetate bath life. After
the P2 assessment, Astroplate installed a DI
water system manufactured by Pure Rain
Technologies, About 420 gallons of DI wa-
ter is used to make up each new bath. In
addition, DI water is added to the bath in
order to make up for evaporative losses.
Spray Rinses: Dragin of process chemicals from preceding
operations was a major source of nickel acetate bath contami-
nation. The P2 assessment determined that dragin could be
reduced by improving preceding rinse operations. Originally,
after anodizing, parts were processed in the black dye tank
and rinsed in a single, flowing rinse before being sealed. Al-
though the rinse water flow rate was 3.6 gallons per minute,
black dye: was dragged in at a rate high enough to discolor the
nickel acetate bath and give it a gray tint. Following the P2
assessment, Astroplate added a spray rinse tank before the
black dye flowing rinse to reduce black dye dragin (see Figure
3). The spray rinse also allows Astroplate to (1) collect con-
centrated black dye rinse water for return to the black dye
bath, which reduces black dye chemical use, and (2) operate
the flowing rinse at a lower flow rate, which reduces water
and sewer fees. Spray system components were obtained from
..Swing Irrigation and Industrial Products of Phoenix, Ari-
zona. The spray system features recessed nozzles whose con-
figuration protects them from damage by racks. In addition,
check valves are used to maintain water pressure in the pipes
connected to the nozzles so that the spray pattern develops
quickly when the system is turned on. The spray system is
activated by a foot pedal.
USING A BATH ADDITIVE
Additives are available for some process baths to replenish
lost chemicals and to introduce chemical agents that boost
bath performance. After the P2 assessment at the facility, an
addtive was identified that is specifically designed to pro-
long the life of nickel acetate seal baths. The additive, which
is called Novaseal Enhancer and is manufactured by'Ndvamax
Technologies, Inc., adds wetting and dispersing agents to
improve seal quality and prevent smut and white powder
formation on parts. The additive also produces a hydropho-
bic anodic coating that helps water to run off parts, thus
minimizing water spotting. Astroplate adds an average of 1.3
gallons of this additive to the nickel acetate bath every week;
the exact amount added in a given week depends on the ob-
served seal quality.
COSTS
The capital and operation and maintenance (O&M) costs
associated with modifying Astroplate's nickel acetate seal
operation are shown in Table 1. These costs are representa-
Parts from
Anodize
DI Water
and Enhancer
Additions
carts to
Nicke
Acetate
Rinses
Filtration
System
Nickel
Acetate
Seal
Flowing
Rinse
Spray Rinse
Figure 2. Nickel Acetate Bath
Filtration System
Figure 3. Modified Black Dye and Nickel Acetate Seal Process Operations
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Capital Cbsts
O&M Costs
Filtzaticn System
Spray System
Spray System
Housing
$1,100
Tferk liner
$911
labor $50/week
Eilbars (6)
$59
Nozzles (30)
$225
Filtration System
Pump
$870
Check valves (6)
$17
labor $25/week
Pressure switch
$115
Piping
$112
Bath Additive Addition
Motor starter
$101
Pressure reducer
$46
Chemical $30/week
Hose and fittings
$258
Foot valve
$133
labor $25/week
Installaticn Mrr
$300
Installaticn Mrr
$1,200
Uttal
$2,803
Uttal
$2,644
DI Water
System and installaticn
$403
Total Capital Cbsts
= $5,850
Total Annual O&M Costs = $6, 760
spent nickel ac-
etate solution de-
creased by 74
percent. During
Phase 1 and 2,
no major
changes in facil-
ity production
levels occurred.
The decrease in
nickel acetate
chemical use,
treatment chemi-
Table 1. Nickel Acetate Bath Life Extension Costs
implementation costs for the P2 techniques used by Astroplate,
except for the cost of the spray system tank liner. Astroplate
needed the tank liner to reinforce an old plastic tank used for
the spray rinse. Therefore, the total cost for Astroplate's spray
system may be higher than for a typical spray system.
RESULTS
Before implementing bath life extension techniques, Astroplate
dumped its nickel acetate bath an average of 2.3 times per
month (or about once every 2 weeks), resulting in a 1,290-
gallon spent nickel acetate solution waste stream each month
(see Figure 4). Astroplate implemented bath life extension
techniques in two phases. Phase 1 involved process bath con-
trol and bath additive use. These techniques were imple-
mented first because of their low capital costs and ease of
implementation. The Phase 1 efforts decreased the average
bath dump frequency to 1.5 dumps per month (or about
once every 3 weeks).
Phase 2 involved filtration system, DI water, and black dye
spray rinse system use. These techniques required more time
to implement because they involved equipment selection,
purchasing, and installation. After Phase 2 implementation,
the average bath dump frequency decreased to 0.6 dump per
month (or once every 7 weeks); the total amount of spent
nickel acetate solution generated each month decreased by
950 gallons to an average of 340 gallons per month. As a
result of the Phase 1 and 2 efforts, the facility's generation of
» 25
E
E 15
E
d 5
Spent Nickel Acetate Solution
Baseline: 1,290 gal./m o
Phase 1: 840 gal. An o
Phase 2: 340 gal./m o
Phase 2
0.6 dump/mo
Phase 1
1.5 dumps/mo
2.3 dumps/mo
5/15/96 7/14/96 9/12/96 11/11/96 1/10/97 3/11/97 5/10/97 7/9/97 9/7/97
cal use, treatment labor, and sludge disposal resulted in an
annual cost savings of $12,130 for Astroplate. The resulting
environmental benefit is a decrease of 56 pounds per year of
nickel released in treatment sludge or discharged in wastewa-
ter.
Astroplate will realize additional cost savings through return
As a result cffefcfr life etfHTStim techniques, Astrqplate
decreased generation c£ spsnfc nickel acetate sdLuticn
ty 74%. The resulting annual cast savings is $22,230.
of black dye spray rinse water to the black dye bath and re-
duced rinse water use in the black dye flowing rinse. The
cost to make up the 550-gallon black dye bath at the facility is
$930. Astroplate can reduce its black dye purchase cost by as
much as $150 per month by returning the spray rinse water
to the process bath.
Bath Life Extension Results
Per Month Annual
Before After Savings
Nickel itetate Chemicals 26 gal 6.8gal $4,140
Treatrrent Chemicals $380 $100 $3,360
Treatrrent Labor 9hcurs 2.4hcurs $3,960
Sludge Generated 150 lb 39 lb $670
Annual Savings = $12,130/yr
Capital Cost = $5,850
Annual O&M Cost = $6,760/yr
Payback Period = capital Cost/ (Savings-o&M Cost)= 1 yr
For more information on this case study or EPA Region 9
P2 projects, contact the following individuals:
Leif Magnuson (EPA)
Les Hunt (Astroplate)
Gail Bliss (ADEQ)
Bill Vins (AESF)
at
at
at
at
(415) 744-2153
(602) 272-9246
(602) 207-4212
(602) 985-9000
Figure 4. Nickel Acetate Bath Dump Frequency and Volume
Assistance for this fact sheet was provided by Terra Tech EM Inc.
E2
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