United States
BOl
EPA-560/11-90-023
•80
Volatile Corrosion Inhibitors
and Boiler Water Additives:
Potential for Nitrosamine Formation
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This document is available through the National
Technical Information Service (NTIS), Springfield,
Virginia 22161, Telephone No. (703) 557-4650.
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CHEMICAL TECHNOLOGY AND ECONOMICS IN
ENVIRONMENTAL PERSPECTIVES
TASK III - VOLATILE CORROSION INHIBITORS AND BOILER
WATER ADDITIVES: POTENTIAL FOR NITROSAMINE FORMATION
by
Alfred F. Meiners
Howard Gadberry
Bonnie L. Carson
Harold P. Owens
Thomas W. Lapp
FINAL REPORT
May 15, 1980
EPA Contract No. 68-01-3896
MRI Project No. 444l-T(3)
For
Environmental Protection Agency
Office of Pesticides and Toxic Substances
401 M Street, S.W.
Washington, D.C. 20460
Attn: Mr. Roman Kuchkuda
Project Officer
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DISCLAIMER
This report has been reviewed by the Office of Toxic Substances, U.S.
Environmental Protection Agency, and approved for publication. Approval does
not signify that the contents necessarily reflect the views and policies of
the U.S. Environmental Protection Agency, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
The report was prepared as part of a preliminary evaluation by EPA and
should not be construed as presenting final Agency judgement concerning the
subject chemicals.
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PREFACE
This report presents the results of a study to develop information con-
cerning volatile corrosion inhibitors.
This study was performed by Midwest Research Institute, as Task III under
Contract No. 68-01-3896 for the Office of Pesticides and Toxic Substances of
the U.S. Environmental Protection Agency. The project officer for this study
was Mr. Roman Kuchkuda. Mr. Charles Auer was the EPA Technical Officer. Princi-
pal Midwest Research Institute contributors to this study included: Dr. Alfred F.
Meiners (Task Leader), Principal Chemist; Mr. Howard Gadberry, Senior Advisor
for Technology; Ms. Bonnie L. Carson, Associate Chemist; Mr. Harold P. Owens,
Associate Industrial Chemist; Ms. Mary Simister, Social Analyst; Ms. Joy McCann,
Junior Scientist; and Mr. Fred Hopkins, Assistant Scientist. Dr. Thomas W.
Lapp is the project leader for this contract, under the supervision of
Dr. Edward W. Lawless, Chemical Impact Assessment Section.
Approved for:
MIDWEST RESEARCH INSTITUTE
B. W. Macy, Acting Director
Center for Technoeconomic Analysi
iii
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CONTENTS
Preface iii
Figures iv
Tables iv
1. Introduction and Objectives . . . 1
2. Summary and Conclusions 3
Volatile corrosion inhibitors 3
Volatile amines in boiler systems .... 6
3. Volatile Corrosion Inhibitors 11
Definition of VCIs and their function n
Compounds used as VCIs 12
Uses of VCIs 17
Market information 19
Theories of the mode of action of VCIs 21
Potential nitrosamine formation in dichan and
related compounds 23
Potential for adverse environmental effects .... 24
4. Volatile Amines in Boiler Systems 27
Boiler water treatment practices 27
Present status of usage of amines in boilers ... 34
Market information 35
Potential for nitrosamine formation in boilers. . . 37
References 41
Appendices
A. Physical properties of VCIs, boiler water amines and
related compounds 47
B. The market for amines and corrosion inhibitors 75
C. Review of possible nitrosamine formation reactions of
VCIs and boiler water amines 81
D. Market information on selected compounds used for
corrosion inhibition 87
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FIGURES
Number Page
3-1 Thermal Stability of Dichan 23
TABLES
Number Page
2-1 U.S. Market for VCI Products, 1978 . 4
2-2 Estimated Consumption of Neutralizing and Filming
Amines 7
3-1 Major Uses of Benzotriazole Compounds ........ 16
3-2 U.S. Market for VCI Products, 1978 . 20
4-1 Recommended Characteristics of Boiler Feedwater ... 29
4-2 Recommended Characteristics of Boiler Water 30
4-3 Quantities of Amines Required to Obtain Particular
pH Values in Pure Water 33
4-4 Estimated Consumption of Selected Amines as Boiler
Water Additives 36
B-l Estimated use of Vapor Phase Corrosion Inhibitors
by Industry 76
B-2 Estimated U.S. Sales of Chemicals and Formulated
Chemical Specialities in Refining, Gas Conditioning
and Pipeline Transmission, 1977— 78
B-3 Comparison of Nace and Kline Surveys Concerning
Corrosion Inhibitors (Millions of Dollars)
79
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SECTION 1
INTRODUCTION AND OBJECTIVES
The Environmental Protection Agency (EPA) has expressed concern that po-
tentially carcinogenic nitrosamines may be formed from the use of secondary
amines* as components of volatile corrosion inhibitors (VCIs). Recent reports
have shown that nitrosamines are formed when secondary amines are incorporated
into plastic wrapping materials for metal products. Nitrosamines have also
been detected in commercial samples of similar wrapping materials. Recent re-
ports have stated that substitutes are being developed for these products be-
cause of the nitrosamine problems. Relatively large quantities of volatile
amines are also known to be used as boiler water additives. Another concern
was the possible use of amines in boilers with nitrate or nitrite salts,
thereby resulting in the potential for nitrosamine formation.
This study was initiated to provide information concerning the materials
which are used for these purposes, the quantities which are consumed, and the
possibilities for nitrosamine formation.
According to most industry sources, the term "volatile corrosion inhibi-
tor" refers to compounds that can volatilize and protect metal surfaces ex-
posed to air or other corrosive gases. It might be more accurate to describe
VCI as "vapor phase corrosion inhibitors." Relatively few compounds can func-
tion as true VCIs, and almost all of these are secondary amine derivatives;
however, hundreds of other compounds (including a wide variety of amines) are
used in corrosion protection applications where a degree of volatility may be
desirable.
Chemicals which are commonly used as VCIs are not normally used as boiler
water additives. A number of secondary amines and other volatile compounds
are employed as neutralizing agents and film-forming materials in the treat-
ment of boiler water. Thus, the primary function of the boiler water amines
is distinctly different from VCIs. The volatility of the boiler water amines,
specifically their ability to steam distill, simply allows them to be intro-
duced into the boiler and transferred through the system to the area which re-
quires corrosion protection, i.e., the area where the steam condenses to give
a liquid-metal interface.
This report is divided into four major sections. Section 1 presents an
introduction to the report and outlines the program objectives. Section 2
A secondary amine has two organic groups and one hydrogen atom attached
to the nitrogen atom (
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contains a summary and conclusions. Section 3 provides data concerning VCIs.
Section 4 presents a discussion of the use of volatile amines in boiler sys-
tems. There are four appendices: Appendix A contains descriptions of the
physical properties of VCIs, boiler water amines, and related compounds; Ap-
pendix B reviews the overall market for amines as VCIs; Appendix C reviews
possible nitrosamine formation reactions of VCIs and boiler water amines; and
Appendix D contains available market information on VCIs, boiler water amines,
and related products. This information was obtained from nonconfidential in-
formation submitted to EPA by manufacturers and importers as of January 1979.
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SECTION 2
SUMMARY AND CONCLUSIONS
A summary of the results obtained in this study is presented in this
two-part section. The first part summarizes the investigation of VCIs, and
the second part summarizes the study of the use of amines in boiler systems.
VOLATILE CORROSION INHIBITORS
The semantics of VCIs is not totally clear, but the term is generally
recognized to mean a chemical substance that by virtue of its volatility at
room temperature reaches a metal surface in need of corrosion protection.
Although a large number of volatile products have been used as VCIs in
the past, the major products at present are dicyclohexylammonium nitrite
(Dichan), "nonnitrite" substitutes for Dichan (in which the nitrite has been
replaced), and benzotriazole.
Dichan (Dicyclohexylammonium "Nonnitrite" Dichan substitute
nitrite) (substituted benzoate salt of
dicyclohexylamine )
Benzotriazole
Industry sources indicate that Dichan has recently been substantially re-
placed by nonnitrite VCIs. The structures of these products are proprietary,
but apparently they are salts of dicyclohexylamine, probably substituted ben-
zoic acid salts in which the substituted benzoate ion has replaced the nitrite
ion of Dichan.
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Benzotriazole is a VCI which inhibits the corrosion of copper. As a VCI,
it is used almost exclusively in impregnated paper. Benzotriazole has many
applications other than as a corrosion inhibitor; most of the production quan-
tities in the United States are probably used in photographic processes.
Market Information
The present market for VCI products is approximately 310,000 kg/year
(Table 2-1) and appears to have remained at this level for the last few years.
The products have been on the market in the United States for at least 25
years but have never substantially exceeded the present volume.
TABLE 2-1. U.S. MARKET FOR VCI PRODUCTS, 1978
Amount of VCI used (x 10^ kg/yr)
Impregnated paper
and other wrapping All other VCI
Compounds materials applications
Dichan (dicyclohexyl-
aramonium nitrite 95 14
Benzotriazole 30 0
"Nonnitrite" VCIs 170 2
Totals 295 16
Source: MRI estimates•
Uses
Over 90% of the use of these products is in the preparation of impreg-
nated paper and other wrapping materials. Impregnated paper is widely used
for the protection of small metallic objects during storage and shipment.
Impregnated paper is also used to protect relatively large items, for example,
stacks of black plate (untinned steel) and tin plate used in the manufacture
of cans. A relatively new VCI product on the market is an impregnated plastic
film for wrapping.
VCIs are also used in applications in which the solid product is placed
within the item it is designed to protect. Many "devices" have been developed
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for this purpose. Formerly, the products were used to protect equipment
within the holds of cargo vessels during shipment, but this application has
apparently greatly declined or even disappeared.
Mechanism of Action
Although the mechanism of VCI inhibition has not been studied in detail,
the protection is apparently due to adsorption of a film on the metal surface.
This film protects against the corrosive effects of water and/or oxygen.
Nitrosamine Formation Potential
Dichan, the nitrite salt of dicyclohexylamine, can apparently be con-
verted under ambient conditions to the corresponding nitrosamine. The com-
mercial product can contain significant concentrations (1 ppm) of the nitros-
amine .
NH NO ,, N—J \N-NO + HO
Dichan N-Nitrosodicyclohexylamine
The nonnitrite VCJs-are less likely to be converted to n i.trosami ncs l>o< ;itise
the nitrite salt, a major nitrosatirig reagent, is not available. However,
other secondary amines can be nitrosated under "environmental" conditions via
a number of mechanisms, and the nonnitrite VCIs would be expected to be read-
ily susceptible. (See Nitrosamine Formation Reactions, Appendix C.)
Potential for Adverse Environmental Effects
A large number of people come into contact with VCIs because of their use
in the wrapping of small metallic items. Over 20 million individual items are
wrapped each year in VCI paper (MRI estimate) and these packages ultimately
expose the user to VCI vapor. Production workers involved in the manufacture
of VCIs and VCI-impregnated paper are also exposed. Two cases of nitrosamine
detection in VCI wrapping material have been reported. In one, N-nitroso-
N,N-dibutylamine was found at an estimated concentration of 100 ppm in an un-
identified commercial film. The same researchers prepared a VCI polyethylene
film and found it to contain 90 ppm nitrosomorpholine.
Dichan enters the atmosphere as a VCI, but it probably is not a long-
lived constituent because of its susceptibility to photolysis. However, no
reports were found concerning the nature of its photolytic decomposition
products.
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No reports have been found concerning the environmental effects of sta-
bility in the environment of nonnitrite Dichan substitutes. Dichan substi-
tutes can probably be nitrosated in the environment via a number of mecha-
nisms.
Benzotriazole--
Benzotriazole is likely to be quite stable and persistent in the environ-
ment. However, the perceived potential for environmental contamination has
been small, and the attention paid to it has been negligible. Benzotriazole
apparently cannot be converted to the N-nitroso product.
VOLATILE AMINES IN BOILER SYSTEMS
A number of amines are employed in the treatment of boiler water; the
amines are primarily used as neutralizing agents and film-forming materials.
Thus, their primary function in these applications is distinctly different
from that of true VCIs. Their volatility (or more exactly, their ability to
steam distill) simply allows them to be introduced into the boiler and trans-
ferred through the system to the area which requires corrosion protection,
namely, the area where the steam condenses to form a liquid-metal interface.
The most widely used neutralizing amines are cyclohexylamine, morpholine,
2-diethylaminoethanol, methylpropylamine (relatively new), and a few others.
The total annual market is estimated to be 6,500 to 7,800 metric tons in 1978
(see Table 2-2).
Octadecylamine represents about 95% of the film-forming amine market, es-
timated to be about 5 million pounds in 1978.
Potential for Nitrosamine Formation in Boilers
There is no experimental evidence to indicate whether or not nitrosamines
are formed in boilers as a result of the addition of boiler water amines.
Most boilers are operated under conditions which would (a) limit the possibil-
ity for nitrosamine formation and (b) probably result in the destruction of
any nitrosamine that might be formed. However, under certain circumstances,
the possibility for nitrosamine formation is conceivable. These possibilities
are discussed in the following paragraphs.
Modern High-Pressure Boilers--
Nitrates and nitrites are potential nitrosating agents for boiler water
amines. However, neither nitrates nor nitrites are ordinarily added to boiler
water. For high-pressure boilers such as those used by electric utilities,
high-purity water is essential. Purification procedures include the careful
removal of dissolved solids including nitrates, present at the 1 to 10 ppm
level in most untreated waters. Some purification procedures require deioni-
zation of the water, and this process would remove nitrate and nitrite (as
well as other inorganic ions). However, nitrosamines could possibly be
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TABLE 2-2. ESTIMATED CONSUMPTION OF NEUTRALIZING AND FILMING AMINES
Estimated
1978 consumption
Type of amine (metric tons)
Neutralizing amines
Cyclohexylamine 3,200-3,600
Morpholine 1,800-2,200
2-Diethylaminoethanol 900-1,400
Methylpropylamine 400
All others 200
Total 6,500-7,800
Filming amines
Octadecylamine
All others
Total 2,500
Sources: Stevens (1978) and MRI estimates.
introduced into water by resins used for deionization; samples of deionized
water have been found to contain as high as 250 ng/liter of N-nitrosodimethyl-
amine.
Other potential nitrosating agents are oxides of nitrogen from air.
Nearly complete deaeration of boiler water is ordinarily employed to remove
undesirable dissolved oxygen and carbon dioxide. These procedures would be
expected to reduce greatly the concentration of dissolved nitrogen oxides in
water. In addition, the boilers are operated at high pH (around pH 9 or 10)
which further limits the formation and stability of nitrosamines. The clas-
sical secondary amine-nitrite reaction would not be expected to occur at this
pH although the nitrosation of amines by oxides of nitrogen could occur rap-
idly.
Although there are limited data on the thermal degradation of nitrosa-
mines in water, most of them are known to be thermally unstable, especially at
temperatures in the range of 300°C. Temperatures of 250 to 300°C are attained
in high-pressure boilers and sustained for relatively long periods of time.
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Thus, eventual thermal decomposition of most nitrosamines would be expected
under these conditions. Furthermore, there is evidence that the thermal sta-
bility of some amines is greatly reduced at the high pH values found in boiler
waters.
Medium-Pressure Boilers
Boilers operating in the pressure range of 100 to 500 psi (maximum tem-
perature about 240°C) utilize much different water treatment practice than
higher pressure boilers. It is common for them to utilize a coordinated phos-
phate treatment system that allows operation with zero added caustic or to
maintain the desired pH with very minor caustic additions. Sodium sulfite (or
in some cases hydrazine) may be used as an oxygen scavenger. The use of so-
dium nitrate (at 200 to 400 ppm) to prevent caustic embrittlement is unknown
to all the boiler specialists who were consulted in this study.
Hence, the occurrence of nitrosamines in moderate-pressure boilers is not
likely to be attributable to reactions between organic amines and other chemi-
cals intentionally added to manage these boiler water systems.
Low-Pressure Boilers
There are hundreds of thousands of relatively small, low-pressure boilers
(25 to 200 psi, maximum temperature less than 190°C) in use for heating and
process steam generation. The majority of these boilers are treated inter-
nally by the use of proprietary boiler water additives, which typically con-
tain phosphates, sodium sulfite, and a sludge-conditioning polymer. None of
the boiler compound suppliers contacted were aware of any additives which
presently contain nitrates or nitrites. However, they did caution that some
boiler additives formulated by some of the numerous, small boiler treatment
supply firms could still incorporate nitrates and/or nitrites. The water used
as feed presents another possible source of nitrate. Hence, the possibility
of reaction between neutralizing amines and nitrates or nitrites is at least
possible in some low-pressure boiler systems.
Hot-Water Boilers
So-called "hot-water boilers," used to circulate water to about 77°C for
heating or to generate low-pressure steam at 10 to 12 psi with 100% condensate
return, may employ sodium nitrite as a corrosion inhibitor. These systems are
closed and require no makeup water since losses occur only if leaks are pres-
ent. Chromate corrosion inhibitors are commonly used, but a combination of
sodium nitrite and borate buffer is also widely employed. The water circulat-
ing systems do not use neutralizing or film-forming amines since the proper pH
is maintained by the buffer system. The development of nitrosamines in hot-
water heating systems is regarded as extremely unlikely.
Reports of Nitrosamines in Steam Emission from Boilers--
A recent report concerning a survey for N-nitroso compounds observed that
small amounts (0.002 |Jg/g) of N-nitrosomorpholine were formed in the steam
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condensate from boilers at a plant which produces chemicals for the rubber
industry (Fan, Fajen, and Rounbehler, 1978). The authors were unable to as-
certain exactly how the nitroso compound was formed, but they speculated that
it was most likely formed by the transnitrosation reaction of morpholine with
N-nitrosodiphenylamine produced at this plant and was detected at various lo-
cations within the plant. Morpholine is used at this plant as a neutralizing
amine for the boilers and as a starting material for the manufacture of a vul-
canization accelerator. N-Nitrosomorpholine was also detected at various lo-
cations throughout the plant in bulk samples and in air samples.
A total of 28 different plants were visited and sampled for N-nitrosamine
contamination. Boiler steam condensate was sampled when nitrosamines were de-
tected at other sites in the plant. N-Nitrosomorpholine was found in the
steam condensate at only one plant; the condensate was collected from leaks in
the steamline. Four of the other plants used morpholine in the boilers but
had no N-nitrosomorpholine contamination. No samples of boiler "blow down"
(the small fraction of water which is discharged from boilers for the purpose
of preventing buildup of dissolved solids) were taken at any of the plants,
and no record was made of the operating characteristics of the boilers. The
authors observed that the nitroso compound exists as a contaminant in the mor-
pholine itself and that this fact may account for its presence in the samples
taken. However, nitrosamine formation via a transnitrosation reaction outside
the boiler appears to be the most likely mechanism. Transamination can only
occur when other nitrosamine contaminants are present.
Potential for Adverse Environmental Effects
Very little is known about the potential for environmental effects caused
by the use of amines in boiler waters. However, over 2,700 metric tons of
secondary amines, over 5,400 metric tons of primary amines, and over 900
metric tons of tertiary amines are consumed each year in these applications.
The precise fate of these products is unknown. Evidently, some of them escape
with steam emissions and some are discharged as boiler blowdown.
The discharged secondary amines would be subject to conversion to
N-nitrosamines in the environment by a number of possible mechanisms. How-
ever, no information was found concerning the amounts or kinds of amines dis-
charged from boilers. Also, no information was available that would conclu-
sively indicate that boiler water discharges contain nitrosamines.
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SECTION 3
VOLATILE CORROSION INHIBITORS
This section presents a definition of VCIs and describes specific com-
pounds and their uses. Information concerning the market for VCIs is pre-
sented, and theories of the mode of action are discussed. The possibilities
for nitrosamine formation and the potential for adverse environmental effects
are also discussed.
DEFINITION OF VCIs AND THEIR FUNCTION
Every person contacted during this study and most literature references
were in agreement about the meaning of volatile corrosion inhibitors or the
equivalent term, vapor phase corrosion inhibitors. These terms mean a solid
substance (rarely, a substance in solution) whose vapor pressure is sufficient
in enclosed spaces to protect the metal surfaces upon which the volatilized
substance condenses, i.e., inside a package, a closed storage area, or an
automotive engine.
Uhlig (1971) in Corrosion and Corrosion Control described VCIs as "sub-
stances of low but significant vapor pressure, the vapor of which has corro-
sion-inhibiting properties" that are used to protect steel articles during
shipping and storing.
Volatile and nonvolatile "atmospheric corrosion inhibitors" were dis-
cussed by Putilova et al. (1960). Nonvolatile atmospheric corrosion inhibi-
tors are generally contact inhibitors whose actions are confined to the area
where they are in contact with the metal surface. These can be nearly any of
the compounds used in neutral aqueous solutions, especially alkali nitrites,
e.g., sodium nitrite. Volatile atmospheric corrosion inhibitors are distin-
guished by their ability to protect while in the gaseous or vapor phase and
are, therefore, termed "vapor phase inhibitors." Of the more than 100 dif-
ferent organic compounds tested up to about 1960, salts of amines and amino
alcohols were the best inhibitors.
Wachter and Stillman (1952) defined a "vapor phase inhibitor" as a "com-
pound which inhibits corrosion of metal parts in the presence of water and air
(oxygen) because said compound possesses corrosion-inhibiting properties and
is capable of vaporization under conditions of use with the resultant presence
of these vapors in the vicinity of the metal." These authors recommended the
use of a combination of two compounds, one of relatively high vapor pressure
(e.g., diisopropylammonium nitrite, Dipan) to provide instant protection and
one of lower vapor pressure (e.g., Dichan) to give prolonged protection.
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Products called "vapor phase rust inhibitors," especially Dipan and
Dichan, were developed by the Naval Research Laboratory for use in aqueous,
nonflammable hydraulic fluids to prevent the rusting of ferrous metals in the
vapor spaces of hydraulic systems. Brophy et al. (1951) described this devel-
opment of "Hydrolubes," which were polymer-thickened, aqueous hydraulic fluids
containing at least one glycol, especially ethylene glycol. The formulations
described contained 1.6 to 1.7% Dipan. None of the "Hydrolubes" had proved
satisfactory for prolonged use above 71°C. Zisman et al. (1951) patented
"Hydrolubes" in which Dipan appeared as a "vapor-phase corrosion inhibitor."*
Wachter and Stillman (1952) patented water-glycol hydraulic fluids con-
taining amine nitrites, preferably those of secondary amines such as Dichan or
morpholine nitrite.
In 1951, Shell Development Corporation (Harman et al., 1951) patented an
aqueous metalworking lubricant or coolant containing a mercaptan; some of these
formulations contained 0.05 to 0.5% Dipan.
The use of amine nitrites as VCIs in the 1940's was quickly expanded to
include packaging materials because desiccants and oils were often unsatisfac-
tory for protecting military equipment and replacement parts during storage
under all climatic conditions (e.g., at subzero temperatures, the viscosity of
oils and greases prevent the operation of weapons). Use of the VCIs eliminated
the tedious cleaning necessary when slushing compounds** were used (Baker, 1954)
COMPOUNDS USED AS VCIs
A large number of volatile organic compounds have been examined for use
as VCIs. Most of the earlier published literature was by Japanese and European
scientists (Putilova et al., 1960; Singh, 1976; Takahashi, 1975). The best
VCIs for ferrous metal were found to be salts of dialkylamines and aminoalco-
hols. For nonferrous protection, benzotriazole and mercaptobenzothiazole were
found to be very effective corrosion and tarnish inhibitors (Cotton and Scholes,
1967). Although a number of compounds has been patented as VCIs, only a few
have been produced for commercial use in the United States. At the present
time, the major VCI compounds are Dichan, substitutes for Dichan, and benzo-
triazole. Other amine salts such as dicyclohexylammonium benzoate, diisopro-
pylammonium nitrite, and cyclohexylammonium carbonate have had limited use as
VCIs in the United States. The physical properties of these compounds and
their related nitrosamine derivatives are presented in Appendix A.
Although the early "Hydrolubes" definitely contained the types of com-
pounds recognized as VCIs in the literature, MRI was unable to find
any such substance being used for that purpose today.
Slushing compounds are petroleum-based materials, ranging from light
oils to semisolids, containing inorganic or organic corrosion in-
hibitors (Campbell, 1948).
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VCIs for Ferrous Metals
The protection of ferrous metals represents the largest fraction (over
90%) of the VCI market. At the present time, the market is dominated by Dichan
and closely related compounds, but other compounds are known to be effective
and have been used in the past.
Dichan--
Dichan is one of the most effective and widely used VCI compounds for
ferrous metals. The substance is a white, crystalline salt with a very slight
odor. It is volatile at room temperature with a vapor pressure of 0.0001 mm
Hg at 21°C and is relatively nontoxic (Uhlig, 1971). It is produced commer-
cially by the action of sodium nitrite on the water-soluble phosphate salt of
dicyclohexylamine.
Dichan
Dichan is more suitable than Dipan lor paper impregnation because il is
less volatile (therefore, it lasts longer) and is less soluble (Baker, 1954).
Black and Wachter (1953) of the Shell Oil Company and the Shell Develop-
ment Company, respectively, enumerated the benefits of using Dichan (these are
also benefits of other VCIs of suitable vapor pressure):
1. Dichan gives excellent long-term storage protection.
2. Dichan will provide protection even if the container is damaged enough
to allow entry of moisture vapor.
3. Surfaces of assemblies that cannot be reached by other means are pro-
tected by Dichan's vapor.
4. The application method is clean.
5. Costly and tedious degreasing operations are eliminated.
6. Protection is maintained under widely variable ambient conditions
from arctic to tropical storage conditions.
7. Articles can be inspected easily.
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Dipan--
Dipan has been used as a VCI in the past, but there is no evidence of its
use at the present time. It is a rather volatile compound with a vapor pres-
sure of 0.012 mm Hg at 20°C and is therefore unsuitable for prolonged protec-
tion against atmospheric corrosion. Tt has a flash point of 40°F and thus
would present a fire hazard. Another reason for its lack of use as a VCI is
that although it protects steel, chromium and tin, it attacks copper, bron/c,
silver, aluminum, brass, antimony, Babbitt metal, cadmium, zinc, and lead
(Putilova et al., 1960).
NO,
Cyclohexylammonium Carbonate (CHC) and Other Carbonate Salts--
CHC is an effective VCI for ferrous metals (Lund, 1970). It has been
produced commercially in the United States and Great Britain, but no produc-
tion data were available. It can be used as a powder, but tablets and CHC-
impregnated paper were available in 1964 (Anonymous, 1964). One reason for
its current lack of use is that although it protects aluminum, zinc, chromium
plate on steel tinplate, solder and soldered joints, it i.s very corrosive to
copper, copper alloys, and magnesium (Uhlig, 1971). It also lias a relatively
high vapor pressure of 0.4 mm Hg at 25°C (Stroud and Vernon, 1975).
< WHI
v_/
[C02
H,
Cyclohexylammonium carbonate
Ethanolamine carbonate is another carbonate found to be an effective VCI
(Uhlig, 1971) but is apparently not being used currently as a VCI in the United
States.
Benzoic Acid Salts--
Benzoic acid salts of diisopropylamine, dicyclohexylamine, ethanolamine,
diethanolamine, triethanolamine, isopropylcyclohexylamine, N-ethylmorpholine,
and naphthylamine have been tested and found to give "100% protective action
toward steel" (Putilova et al., 1960). However, these compounds are apparently
not used at the present time as VCIs in the United States.
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Rosenfeld et al. (1972) reported that arnine nitrobenzoates are much more
effective than amine benzoates or amine nitrites as VCIs.
Alternatives--
Although Dichan was very recently the most widely used VCI, several VCI
producers are changing to compounds that do not contain nitrite salts. The
substitute compounds were not identified by the companies; however, patent
literature and trade publications indicate that substituted benzoate salts
(salts in which the anion contains a substituted benzoic acid group, e.g., a
chlorobenzoic acid anion) are the compounds most likely to be used in place of
nitrites. An example of a chlorobenzoate salt is:
Cl
Dicyclohexylammonium chlorobenzoate
VCIs for Nonferrous Metals
Benzotriazole is one of the most effective compounds used as a corrosion
inhibitor for copper and other nonferrous metals such as chromium, nickel-
silver alloys, and zinc-nickel alloys (Sherwin-Williams, 1976). It can be
prepared directly by the action of nitrous acid on o-phenylenediamine and by
the hydrolysis of an acylated or arylated benzotriazole. It is a white to
off-white crystalline powder which melts at 96 to 97°C (Damschroder and
Peterson, 1955).
Much lower levels (about 0.01 to 0.1 as much) of VCI are needed to pro-
tect copper than to protect steel (Schneider, 1978). For example, tissue paper
carrying 2% by weight benzotriazole interleaved between copper mill sheets pre-
vented tarnish for approximately 18 months. A brown wrapping paper coated with
0.43 g benzotriazole/m2 and 10.8 g Dichan/m2 protected copper and steel against
water-saturated air containing 1% sulfur dioxide for 20 hr (Sherwin-Williams,
1976).
Most of the uses of benzotriazole for corrosion inhibition are not as
VCIs. The compound has been used in antifreeze and engine coolants, cleaners,
coatings, detergents, electrolytic processes, hydraulic and other functional
fluids, metalworking processes, polishes and waxes, and water-circulating sys-
tems (Sherwin-Williams, 1976; Schneider, 1978). Table 3-1 shows the major
uses of benzotriazole compounds (Davis et al., 1977).
15
-------
TABLE 3-1. MAJOR USES OF BENZOTRIAZOLE COMPOUNDS
ANTI-CORROSION - antifreeze compositions
hot water heaters and associated pipes of iron, copper,
and their alloys
electric generator water cooling systems
cleaning pastes and polishes
impregnated protective paper (for packing, wrapping, and
storage)
dry cleaning fluids
dishwasher detergent
metal lacquers
hydraulic and lubrication fluids
electrolytic deposition (improves hardness and brightness)
ULTRAVIOLET STABILIZATION - plastics, especially polyolefins
other polymers, such as nylons and polyesters
clear coatings
paints and pigments
oils
PHOTOGRAPHY - antifoggants
emulsion tint agent
UV absorber/stabilizer
thermographic photocopying processes
Source: Davis et al. (1977)
16
-------
Competitors with benzotriazole (I) in some of these applications are
tolyltriazole (II), 2-mercaptobenzothiazole (III), phosphonates, and chromates.
The structures of compounds I, II, and III are show below:
II
III
Benzotriazole is taking over many corrosion inhibitor markets where the
elimination of chromates is desired for environmental reasons (Schneider, 1978).
There are a few uses of benzotriazole as a corrosion inhibitor in consumer prod-
ucts reaching the general public (e.g., hydraulic (brake) fluids and antifreezes)
In addition, a product is marketed which consists of a sponge impregnated with
benzotriazole to be placed unwrapped in a cutlery drawer or chest to protect
silver (Schneider, 1978).
Alternatives--
No alternatives for benzotriazole and tolyltriazole as VCIs were specif-
ically identified.
USES OF VCIs
VCIs are used for corrosion control of both ferrous and nonferrous metals.
Over 90% of the amount presently being used is coated or impregnated in packag-
ing and wrapping materials. VCIs are also currently being marketed as solid
crystalline products in the form of pellets, tablets, and powders, which are
often packaged in small permeable containers.
ing,
VCIs have many applications (Miksic, 1978; Kravik, 1978) in the packag-
shipping, and storage of a wide variety of items including:
Artifacts in museums
Ball bearings
Computers
Electrical transformers
Gasoline engines
Guns
Hearing aids
Marine electronic equipment
Molds
Motors
Piping
Process control devices
Propane tanks
Pumps
Tanks
VCIs are used in cartridges, tablets, or powder form to protect the following
items:
17
-------
Computers
Electrical equipment
Junction circuits
Process control equipment
Switch boxes
The major users of VCIs are discussed in the following paragraphs.
The Military
The principal use by the military and military contractors is for ord-
nance, including storage of weapons, combat vehicles, ammunition, maintenance
tools, and equipment. Small parts are wrapped in VCI paper and sealed in con-
tainers. VCI crystals are placed in the cavities of aircraft engines and tanks
in storage. The present military specification calls for an acceptable test to
determine the effectiveness of compounds used as VCIs, but not their safety.
Dichan and Dipan have been accepted by the military (Carroll, 1978).
The Automotive, Aircraft, and Tractor Industries
These industries are the largest users of VCI paper. The paper is used
to protect small parts, e.g., ball bearings, electrical components, and gears,
which are shipped overseas or stored for a period of months.
Steel and Copper Manufacturers
The steel industry uses VCI paper to wrap "black" plate, which is untinned
steel, and tin plate produced for can companies. Stacks of cut steel plate (3
x 6 ft) on wooden pallets are wrapped with VCI paper. VCI paper containing
benzotriazole is used by manufacturers of copper and other nonferrous products
to prevent tarnish as well as corrosion.
Electrical and Electronic Equipment
VCI crystals in small permeable bags or cartridges are used in switch
boxes and cavities of large electronic machinery located in areas having high
humidity, warm temperature, or a salt water atmosphere (Kravik, 1978). Ben-
zotriazole-treated paper is used to wrap reels of copper wire and electronic
equipment. During subassembly storage, microwave components, electronic com-
puter parts, typewriters, and radio and television circuit boards are protected
by benzotriazole-coated papers. Manufacturers, such as Honeywell, Rockwell
International, General Electric, Westinghouse, and General Motors also use VCI
paper for the protection of metal parts and components.
18
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Uses by the General Public
Currently the bu.lk of VCI paper and crystals is used by industry and not
the general public. However, small amounts are used by individuals in the
storage of tools, guns, and sterling silver (Miksic, 1977; Kravik, 1978).
MARKET INFORMATION
Based on information from numerous industrial sources, the total market
for VCI products is estimated to be between $7 million and $8 million per year.
Approximately 311,000 kg/year of various chemicals are used as VCIs (see Table
3-2). Appendix D contains market information on VCIs and related products ob-
tained from nonconfidential information submitted to EPA by manufacturers and
importers as of January 1979. Until very recently, the market was dominated
by Dichan,** but this product is rapidly being replaced by "nonnitrite" VCIs .*
By far the largest share of the market is represented by impregnated paper and
other wrapping materials; apparently the market for impregnated paper is much
greater than for other wrapping materials such as impregnated plastic films.
The size of the overall market has been stable for the past 4 to 5 years
despite a reduction of VCI purchases by the military (Bell, 1978); this reduc-
tion has been offset by the growth of the VCI paper market.
The development of impreganted plastic wrapping material will probably be
a significant factor affecting the future growth of the VCI market, in partic-
ular, the development of "cold seal" films of polyesters which are impregnated
with VCI compounds is significant. These products will provide a transparent
package which seals out moisture arid gives corrosion protection. At the pres-
ent time, these products are produced only by the Orchard Paper Company and
sold as "Rapid Seal" (Van Winkle, 1978).
VCI-Impregnated Paper and Other Wrapping Materials
The market for VCI-impregnated paper is estimated by industry sources to
be between $6 million and $7 million (Hutter, 1978). No production figures
were available on the amount of each VCI compound used in this application.
A discussion of the overall market for volatile amines as corrosion in-
hibitors is presented in Appendix B.
Boris Miksic, Chairman of the Volatile Corrosion Inhibitors Group
(T-3A-4) of the National Association of Corrosion Engineers (NACE)
in a letter to Norbert Page of NIOSH (January 1977) stated that he
believed that the market for VCI compounds was "over 10 million pounds
per year" (4,500,000 kg/year). Our contacts with manufacturers and
users of these products have indicated that the market is less than
one-tenth that size.
"Nonnitrite" VCIs are proprietary substitutes for Dichan (dicyclohexyl-
ammonium nitrite) in which the nitrite anion has been replaced with
another anion, for example, a substituted benzoate anion.
19
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TABLE 3-2. U.S. MARKET FOR VCI PRODUCTS, 1978
Amount of VCI used (thousands of kg)
Impregnated paper
and other wrapping All other VCI
Compounds . materials applications
Dichan (dicyclohexyl- 95 14
ammonium nitrite
Benzotr lazo I.e '!() 0
"Nonnitrite" VCIs , 170 _2
Total 295 16
Source: MRI estimates.
However, the total market can be estimated from the average loading factor,""
11 g/m2 (1 g/ft2) and the average cost of VCI paper, 24C/m2 (20C/yard2); thus,
over 27 mi.ll.ion m2 (30 million yard2) of VCI paper is produced per year ntil-
i/ing an esL.imat.ed 295,000 kg of VCI chemicals. According to flutter (1978)
approximately one-third of this amount, or ahout 9!>,00() kg, is Dichan, and 11%,
or ahout 30,000 kg, is benzotriazole. The remainder, about 170,000 kg, is es-
timated to be "rionnitrite" VCIs which have been used in place of Dichan (Hutter,
1978).
Daubert Chemicals, the main producer and user of the nonnitrite VCIs, con-
siders the identity of the compounds and the amounts produced to be proprietary.
However, the information in the patent literature and trade publications indi-
cates that substituted benzoate salts of dicyclohexylamine and other fatty
amines are the likely replacements for nitrite salts.
There are three major VCI paper companies: Daubert Chemicals, which is
estimated to have 80% of the market; Ludlow Corporation, 15%; and Cromwell,
5%. Mead, Scott, and International paper companies are firms which buy small
amounts of VCIs for more specialized products such as tissue for rolling sheet
and excelsior for drums holding copper fittings (Schneider, 1978).
The loading factor is the amount of VCI ordinarily used in the manufac-
ture of impregnated paper.
20
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VCI "Crystals"
Solid VCIs used for applications other than impregnated paper are referred
to as "VCI crystals." The VCI crystal market is estimated to he slightly less
than $1 million, which is equivalent to about 16,000 kg. Dichan represents
about 85% of this market. The Olin Corporation is the major producer of Dichan
crystals, which are marketed (as VP1® 260) by the Shell Chemical Company to
small customers. The Alcon Company of New Orleans, Louisiana, also produces
Dichan and is a major supplier to the military.
Benzotriazole
As indicated previously, the amount of benzotriazole used annually as a
VCI in paper was estimated to be 30,000 kg (Hutter, 1978). This amount is con-
sistent with an annual VCI paper production of 27 million m2 and a loading fac-
tor of 1 g/m2 (0.1 g/ft2).
U.S. producers of benzotriazole are Sherwin-Williams, Eastman Kodak,
Fairmount Chemical, Columbia Organic, Mobil Oil, and Sieflor (Appendix D).
Although Eastman Kodak sells benzotriazole through its Organic Chemicals
and Photographic Chemicals Divisions, quite probably most of the benzotriazole
is produced for captive use in photographic processes. The Organic Chemicals
Division sells benzotriazole as a laboratory chemical in small packages through
dealers. Only two companies, whose names were not revealed, have bought benzo-
triazole in large amounts. The Eastman Kodak representative did not recognize
these two firms as users of corrosion-inhibiting chemicals (Van Sice, 1978).
Cross (1978), Vice President of Marketing at Fairmount Chemical Company,
had no idea what the total U.S. production of benzotriazole is at the present
time. Fairmount produces benzotriazole for photographic use but has been un-
able to penetrate the copper protection market held by Sherwin-Williams (Cross,
.1978). Since Sherwin-Williams is the major producer and has a big share of
the market, the U.S. International Trade Commission does not report benzotri-
azole production figures.
Schneider (1978), Product Manager for Triazole Products at the Sherwin-
Williams Company, Chemical Division, estimated that world use of benzotriazole
as a VCI was 68,000 kg (150,000 Ib) in 1978. Complicating the estimate for
U.S. consumption for that purpose is the possibility that a few companies may
import benzotriazole to sell as a corrosion inhibitor. Although several for-
eign patents on benzotriazole as a corrosion inhibitor have been issued to
American Hoechst Corporation, the company stated that none of the benzotriazole
produced by the parent firm is imported for sale in the United States (Swift,
1978).
THEORIES OF THE MODE OF ACTION OF VCIs
Uhlig (1971) stated that the mechanism of VCI inhibition had "not been
studied in detail" but that protection is apprently due to adsorption of a
film on the metal surface that protects against water and/or oxygen.
21
-------
Nitrite ion may be supplied by the volatile nitrites to passivate* the metal
surface.
According to Rosenfeld et al. (1972), the effectiveness of a compound em-
ployed as a VCI depends on its saturated vapor pressure, its capacity to be
adsorbed by the metal surface, and the presence of functional groups capable
of passivating the metal surface.
Trabanelli and Zucchi (1976) and Trabanelli et al. (1967) have reviewed
some of the theories which have been postulated concerning the mechanism by
which VCIs protect against corrosion:
* The inhibitor saturates the atmosphere surrounding the metal surface,
reducing the relative humidity at the metal-gas interface below a
certain critical value.
* The adsorbed inhibitor renders the metallic surface hydrophobic,
thereby preventing contact of the metal with moisture in the atmo-
sphere.
* The inhibitor produces a strong electrical resistance on the metal
surface which reduces the corrosion current.
* The inhibitor renders the metal surface alkaline causing the cor-
rosion rate to become negligible.
* The inhibitor causes passivation of the metal surface by saturating
the metal-gas interface with inhibitor and by polarizing the metal.
Very little information is available concerning the mechanism by which VCIs
prevent corrosion. However, the following observations are significant. Black
and Wachter (1953) stated that since Dichan (dicyclohexylammonium nitrite) is
moderately water-soluble, its protection ability cannot be attributed to forma-
tion of a hydrophobic-adsorbed film. The pH of aqueous solutions of Dichan is
near 7, so its action cannot be ascribed to the development of an alkaline pH.
Dichan does not react detectably with oxygen, so it cannot be an oxygen scav-
enger. It is not especially hygroscopic, so its action cannot be that of a
desiccant. Thus, the most reasonable mechanism for the VCI properties of
Dichan is that its volatility serves as a means of transport to the metal sur-
face where it contributes a nitrite ion (a recognized contact corrosion inhib-
itor) to condensed or adsorbed moisture on the metal surface (also in Wachter
et al. , 1951).
Passivation is a process in which the corrosion of a metal surface is
inhibited by the formation of an insoluble compound by precipitation
or reaction. Anions of weak acids, e.g., nitrite, chromate, benzoate,
silicate, phosphate, and borate, form passivating films that stabilize
the metal oxide coating (Uhlig, 1971).
22
-------
The mechanism of "nonnitrite" VCIs is probably similar, except that the
nitrite ion is replaced by a substituted benzoate ion.
Benzotriazole is thought to form a 1:1 chemical complex with copper ions
on the copper surface. This reaction results0in the formation of a highly im-
permeable physical barrier layer 50 to A,000 A thick (Sherwin-Wi 1 1. i;ims, 1076).
POTENTIAL NITROSAMINE FORMATION IN DICHAN AND RELATED COMPOUNDS
The major VCI, Dichan, would be expected to be especially vulnerable to
nitrosamine formation because it is a nitrite salt of a secondary amine. As
described in Appendix C, "Nitrosamine Formation Potential," secondary amines
are readily nitrosated by nitrous acid or nitrite under a wide variety of con-
ditions. However, little published information was found concerning the con-
version of Dichan to the corresponding nitrosamine.
An early experiment on the chemical and thermal stability of Dichan
(Wachter et al., 1951) showed the possibility for nitrosamine formation. How-
ever, nitrosamines were not considered a serious hazard at that time, and the
extent of nitrosamine content during decomposition studies was not measured.
Dichan was considered "remarkably stable"; a plot of years required for
total decomposition versus temperature is presented in Figure 3-1.
10 21
32 43 55 66
Temperature, °C
77
Source: Wachter et al. (1951)
Figure 3-1. Thermal stability of Dichan.
23
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For the study of the pure crystals, Dichan was sealed in glass tubes and
stored at different constant temperatures for extended time periods. A
variety of Dichan coated and impregnated papers were stored separately in
waxed paper envelopes in a closed box at room temperature (about 72°F) for
periods of 1 to 3 years.
The Dichan content of the crystals and the paper was measured on the basis
of the nitrite content. The observed decreases in nitrite content could have
been the result of the conversion of Dichan to the nitrosamine or the nitrate
salt; however, no attempt to detect either of these products was reported.
Recent information obtained from an industrial source indicates that com-
mercial Dichan contains "extremely low" amounts of nitrosamine. These amounts
were not quantified but were said to be less than 1 ppm (Palm, 1978).
Nitrosatnines from Benzotriazole
The preparation of benzotriazole and its derivatives is from the appro-
priately substituted o-phenylenediamine and nitrous acid. The photographic
grade of benzotriazole is almost 100% pure, and the purity of the technical
grade is 99.7 to 99.8% (Schneider, 1978).
Nitrosation might occur under the reaction conditions so that even when
used without nitrite some nitrosamine could be present. However, Schneider
(1978) stated that Sherwin-Williams had not been able to form the nitrosamine
of benzotriazole under conditions such as varying the pressure, temperature,
and nitrogen oxide concentration. However, the firm now recommends that so-
dium nitrite not be used with benzotriazole.
POTENTIAL FOR ADVERSE ENVIRONMENTAL EFFECTS
Little is known concerning the stability of VCI products in the environ-
ment. Dichan is known to be thermally unstable (Shell, 1972; Wachter et al.,
1951). .It is also known to be extensively decomposed by sunlight (20 to 50%
decomposition in 60 days) (Wachter et al., 1951). As a VCI, Dichan enters the
atmosphere where it is probably not a long-lived constituent because of its
susceptibility to photolysis. However, no studies have been found concerning
the nature or toxicity of its decomposition products.
Also, no reports have been found concerning the environmental effects or
stability in the environment of Dichan substitutes or benzotriazoles.
As pointed out earlier, the biggest use of VCIs is in wrapping materials,
especially impregnated paper. Archer and Wishnok (1976) detected N-nitroso-
N,N-dibutylamine in a sample of "commercially produced, corrosion-resistant
film of unknown composition." The concentration was estimated to be about 100
ppm. However, no indication was found that dibutylamine or any of its salts
are actually used in products of this kind. Also, Wishnok stated that he did
not know the commercial source of the sample, nor had their group done any fur-
ther studies since the one which was published. The dibutyl nitrosamine was
"tentatively" identified by a highly reliable analytical methodology, gas
24
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chromatography-mass spectrometry. Archer (1978) stated that the supplier of
the sample had responded that the identified compound was not one which could
be expected.
Archer and Wishnok also prepared "a corrosion-resistant polyethylene film
with a surface layer of morpholinium nitrite in an acrylic binder covered with
a layer of latex." This film was subsequently (time unspecified) found to con-
tain nitrosomorpholine. The nitrosamine concentration of a methylene chloride
extract of the film was 90 ppm. These investigators also found 3,000 ppm of
nitrosamine in an "unpurified" sample of the morpholinium nitrate which they
prepared by a procedure in which carbon dioxide was bubbled through a mixture
of morpholine and sodium nitrite in methanol.
Benzotriazole in contact with air, water, or sunlight is likely to be
quite stable and persistent. However, the perceived potential for environ-
mental contamination has been small, and the attention paid to it has been
negligible (Davis et al, 1977).
25
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SECTION 4
VOLATILE AMINES IN BOILER SYSTEMS
VCIs such as Dichan are not used in steam boilers; the compounds are too
expensive and would probably be decomposed by the high temperatures (Wachter
et al., 1951; Baker, 1954). However, a variety of volatile and nonvolatile
amine compounds are employed to control corrosion in boilers. Also examined
is the possibility that amines added to boilers might form nitrosamines
through reaction with nitrites, nitrates, oxides of nitrogen, or any other ni-
trosating agent. The market for boiler water amines is also discussed.
This section of the report considers the current range of chemical prac-
tices used to manage boiler water in heating, process steam generation, and
electrical power production.
BOILER WATER TREATMENT PRACTICES
The water used in boilers is treated by: (a) removing dissolved solids
that would form adherent scale (softening or deionization); (b) removing dis-
solved gases, including oxygen and carbon dioxide; (c) adding alkali to main-
tain a desirable pH; and (d) introducing chemical agents that act as oxygen
scavengers, neutralize carbon dioxide in the condensate, serve as passivators
or corrosion inhibitors, and maintain precipitated sludge in a suspended con-
dition. The sections which follow consider the water management practices
that are typical for boilers operating from low pressure to super-critical
pressures, with special emphasis upon the use of amines and any potential ni-
trosating agents.
The extent of pretreatment required for boiler feedwater and the type of
compounds used to prevent scale formation, embrittlement, and corrosion are
largely dictated by the type of boiler employed and its operating pressure.
One convenient, though arbitrary, classification of boiler types is shown be-
low (Hamer et al., 1961):
Maximum
Boiler Pressures (Ib/in ) Temperatures (°G)
Low-pressure Up to 200 190
Intermediate-pressure 200 to 500 240
High-pressure 500 to 2,000 335
Very high-pressure 2,000 to 3,209 375
Super-critical Above 3,209 375
27
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Feedwater Requirements
The requirement for feedwater purification becomes more stringent as the
operating pressure increases. The concentration of dissolved solids in high-
pressure and very high-pressure boilers must be held to much lower levels than
for low-pressure or intermediate-pressure boilers. Table 4-1 gives the gen-
eral characteristics typically required for feedwaters. Typical properties of
the corresponding boiler waters are shown in Table 4-2.
Very large numbers of low-pressure boiler systems—these include rela-
tively small heating systems and moderately sized industrial boilers—are op-
erated with minimal pretreatment of the feedwater. Precipitation or exchange
softening may be used, or proprietary boiler compounds may be added to the
feedwater to achieve what is termed "internal treatment" in which all chemical
treatment of the water is carried out entirely within the boiler system it-
self.
Internal treatment is widely used for the smaller and simpler boilers,
such as the various types of shell boilers, but under certain conditions can
also be used for watertube boilers. This type of treatment requires the main-
tenance of an adequate excess of sodium carbonate or phosphate in the boiler
water to precipitate substantially all of the hardness in a form which will
not adhere to boiler surfaces.
Most boilers designed to operate above 200 lb/in2 utilize preliminary
treatment of water to remove hardness and scale-forming impurities. For
larger boilers, the use of demineralization or evaporation to provide high
purity feedwater is widespread.
Oxygen Removal
After pretreatment, feedwater is treated to remove oxygen. The usual
practice is to subject feedwater to physical deaeration by bringing it into
contact with steam in the feed heater. An effective deaerator will reduce the
dissolved oxygen to about 0.07 ppm (70 ppb) or less. Alternatively, the water
may be held in the feedwater tank at 90 to 95°C for a period of 30 min to re-
duce dissolved oxygen to about 2 ppm. This type of oxygen removal is prac-
ticed on smaller, less elaborate boiler systems operating at 250 lb/in2 or
less.
Oxygen is further removed by the use of chemical reducing agents. The
.most important oxygen scavengers are sodium sulfite and hydrazine (Francis,
1962). Although other compounds have been reported in the literature, the
boiler experts and operators interviewed in this study did not report using
any other agents.
Sulfite—
Sodium sulfite reacts with oxygen to form sodium sulfate:
28
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TABLE 4-1. RECOMMENDED CHARACTERISTICS OF BOILER FEEDWATER
Type of boiler
Recommended characteristics
Hardness
(expressed as calcium
carbonate)
(ppm)
Alkalinity
Oxygen content
Remarks
Low-pressure
(up to 200 lb/in2)
Medium-pressure
(200-500 lb/in )
vo
< 20
< 10
Sufficient to give
pH value of 9.0
or greater
Sufficient to give
pH value of 9.0
May occasionally be
necessary to reduce
to below 0.14 ppm
0.007-0.03 ppm
Corrosion of feed systems is usually prevented
by maintaining correct alkalinity in feed-
- water; corrosion of boiler is prevented by
alkalinity control and by various mechani-
cal arrangements for discharging gas into
the steam space. Where oxygen content must
be reduced, physical deaeration is used.
Good physical deaeration may be sufficient to
give desired oxygen content; if not, sodium
sulfite or hydrazine are added.
High-pressure
(500-2,000 lb/in )
< 1
As for medium-
pressure boilers
Nil
Good physical deaeration followed by contin-
uous addition of sodium sulfite or hydra-
zine is essential.
Source: Hamer, Jackson, and Ttmrston, 1961.
-------
TABLE 4-2. RECOMMENDED CHARACTERISTICS OF BOILER WATER-
a/
Hardness
(expressed as Sodium phosphate
calcium carbonate) reserve (expressed
Type of boiler (ppm) as P04) (ppm)
commended characterist
Alkalinity
Silica
Alternative treatment chemicals _tg prevent caustic cracking Sodium sulfite content Dissolved
Sodium sulfate Sodium nitrate- excess (ppm) (ppm) solids
content . content Phosphate content as such as such (pp«n)
Remarks
Low-pressure -^5 when carbonate
(up to 200 Ib is used.
lb/in2)
2 when phospha
30-90C Carbonate alkalinity Sufficient to give
(where used) should be S 200 Na2S04/NaOH
ppm expressed as weight ratio
calcium carbonate $ 2"5 and pref-
and probably
> 300 ppm.
erably > 3-0 in
boiler water.
Sufficient to give Sufficient to gi'
ratio of NaN03 coordinated
to total alka-
linity (includ-
ing phosphate if
present) ex-
pressed as NaOH
S 0-4 in boiler
phosphate treat-
ment, but rarely
used in low-
pressure boilers.
50-200
'.where used)
Any
3,000-
20,000
Dissolved solids depend
type of boiler,d
Medium-
pressure
(200-500 Ib
lb/in2)
30-90C
Sufficient to give
pH value of 11
or more;6 alkali
content S 10% of
dissolved solids.
As for low-
pressure
boilers.
As for low-
pressure
boilers.
Sufficient for co-
ordinated phos-
10,000- Dissolved solids 'figures apply
3,000 to watertube boilers and
creases. Suspended solids
High-pressure
(500-2,000
As for medium*
pressure boilers.
As for low-
pressure
boilers.
As for low-
pressure
boilers.
As for medium-
pressure
boilers.
3,000-
1,000
safety from turbine blade
deposits, but higher fig-
ures are often acceptable.
d Figur.
follows:
Lancashire boiler
Economic boiler
Locomotive boiler
20,000 ppm
15,000 ppm
4,000 ppm
3,000 ppm
e Measured at atmospheric temperature,
f Sodium sulfite excess depends primarily on efficiency of initial mechanical deaeratlon (including that due-to retention in hot
feed tank). If mechanical deaeration is efficient and reliable, relatively low sodium sulfite excess only is required.
res apply
s, and
e in-
also be take
nto account.
Fig
appear to giv*1 complete
saftty from turbine blade
deposits, but higher fig-
a For reccxonended characteristics where internal treatment is used, see text.
b Measured by EDTA method.
c Typical values; reserve depends on possible rate of depletion and frequency of replenishment. Large quantities may be required where coordinated phosphate treatment
is used.
Source: Hamer, Jackson, and Thurston, 1961.
-------
2 Na SO + 0 - -2'Na SO
Sulfite is generally used as an oxygen scavenger for removal of oxygen from
water that has been physically deaerated. Preliminary scrubbing to remove
oxygen is essential, both to reduce the cost of chemicals and to prevent an
undue buildup of dissolved solids content of the boiler water.
There are certain objections to the use of sodium sulfite as a deoxygen-
ator, apart from the fact that it cannot be used without increasing the dis-
solved solids content of the boiler water. A more important objection is its
liability to decompose at the higher boiler pressures to form hydrogen sulfide
or sulfur dioxide. The fact that sodium sulfite does decompose in operating
boilers seems to be established. As a general rule, sodium sulfite can be
safely used as an oxygen scavenger in boilers working at pressures up to at
least 1,000 lb/in2, provided that the boiler water is alkaline and the con-
centration of sulfite is not above about 10 ppm (Na2S03).
Hydrazine--
Hydrazine is a powerful reducing agent which reacts with dissolved oxygen
under boiler conditions as follows:
N2H4 + °2 -- * 2 H2° + N2
It is thus capable of removing oxygen from the boiler water without increasing
the dissolved or suspended solids content (Fletcher, 1958; Woodward, 1958).
Hydrazine also decomposes under boiler conditions:
The formation of ammonia from the hydrazine is regarded as advantageous in
reducing the risk of corrosion by dissolved carbon dioxide in condensate.
As shown in the equation, one molecule of hydrazine is needed to remove
one molecule of oxygen. In practice, however, a 100% excess of hydrazine in
the feedwater is generally used so as to ensure rapid removal of the oxygen.
Prevention of Caustic Embrittlement--
Sodium nitrate was formerly added to boiler water to prevent caustic em-
brittlement.* Boiler experts were almost unanimous in pointing out that the
occurrence of caustic embrittlement problems today is so rare that the embrit-
tlement problem and chemical treatment to avoid it have all but disappeared
(Thiedke, 1978; Johnson, 1978; Walters, 1978). Walters (1978) stated that
nitrates have not been included in boiler compounds since about 1960. Thiedke
Caustic embrittlement is the term used to describe the weakening of
ferrous alloys which occurs when the alloys are under stress and
exposed to caustic.
31
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suspected that compounds offered by some of the smaller firms might still con-
tain nitrates as a precautionary measure (Thiedke, 1978).
Coordinated phosphate treatment—Conditioning of carefully purified feed-
water to maintain the desired pH at "zero-caustic" conditions is the most com-
mon means of avoiding caustic embrittlement. The technique is employed for
boilers in the 500 to 1,800 lb/in2 range (Fryling, 1966; Purcell and Whirl,
1942). This treatment involves adding sufficient acid sodium phosphate to the
boiler water.
Chemical Treatment of Condensate Systems —
Condensate systems can be chemically treated to control corrosion damage
caused by water and carbon dioxide. The treatment chemicals consist of neu-
tralizing amines, filming amines, hydrazine, and, in many cases, ammonia.
Neutralizing amines—When condensate is to be used as feed for boilers,
it is often necessary to reduce the pickup of iron so that the iron content is
less than 0.01 to 0.1 ppm, depending on pressure. The pH level of the con-
densate should then be kept at about 9 by injecting a soluble neutralizing
amine into the boiler feed or the steam line. The amine volatilizes with the
steam and combines in the condensate with the carbon dioxide to form bicarbo-
nates or carbonates. On returning to the boiler, the amine carbonates decom-
pose to reform the amine and carbon dioxide. The process is to some extent
then repeated. Losses occur through blowdown and leakage.
The compounds used for this purpose include ammonia, cyclohexylamine,
morpholine, 2-diethylaminoethanol, methylpropylamine, and others (Hamer et al.,
1961). The physical properties of these amines are presented in Appendix A.
The use of ammonia has sometimes been considered objectionable since, espe-
cially in the presence of small amounts of oxygen, it can cause the corrosion
of equipment made of copper or copper alloys. Ammonia is widely used, how-
ever, and corrosion of copper is prevented by maintaining the dissolved oxygen
content of the feedwater at very low levels. Cyclohexylamine and morpholine,
on the other hand, do not cause such corrosion, at least at the concentrations
employed for preventing corrosion of ferrous metals.
The choice between ammonia and one or another of the organic amines de-
pends on the quantities required and, hence, on the cost. The requirements
depend on their relative basic strengths and volatilities. Under working con-
ditions, very much smaller amounts of ammonia than of the organic amines are
needed to raise the pH value of pure water by a given amount; furthermore, the
price of a unit weight of ammonia is very much lower than that of either of
the liquid amines. These advantages of ammonia are to some extent offset,
however, by the fact that the volatility of ammonia in steam is so high that
in some plants a large proportion will remain in the vapor phase and the de-
sired effects of raising the pH value at the point where condensation first
takes place will not occur unless large amounts of ammonia are used. Ammonia
appears to provide the cheapest and most effective method of protecting con-
densate systems from corrosion, provided that the oxygen content is low so
that attack on copper equipment can be disregarded.
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The choice between cyclohexyLamine and morphol ine is difficult Lo re-
solve. Both amines appear to be equally stable substances; each amine decom-
poses under boiler conditions at temperatures above 370°C (Archibald et al.,
1953). On the other hand, more recent work (Feitsma, 1958) suggests a de-
composition temperature at 266°C for morpholine and 288°C for cyclohexylamine.
Both have been used successfully (Rivers and Sonnett, 1950; Corey, 1947) in
boilers operating at pressures up to about 1,500 lb/in2. Their boiling points
are close together—cyclohexylamine boils at 134°C and morpholine at 129°C--
and their volatilities might accordingly be expected to be similar. Cyclo-
hexylamine forms a constant boiling mixture (azeotrope) with water at 97°C,
and this provides it a volatility in steam about 10 times greater than that of
morpholine, which forms no azeotrope. Thus, morpholine condenses out more
completely than cyclohexylamine at the point where condensation first takes
place. However, cyclohexylamine is the stronger base of the two and is much
more capable than morpholine of raising the pH level of condensate when it is
present in equal quantities. The high volatility of cyclohexylamine also im-
plies that the available reserve in the boiler water will be smaller than with
morpholine for any given amine dose in the steam. Table 4-3 presents typical
concentrations.
TABLE 4-3. QUANTITIES OF AMINES REQUIRED TO OBTAIN PARTICULAR
pH VALUES IN PURE WATER
Amine
Conditions
Amount needed
Ammonia
Cyclohexylamine
Morpholine
C02 absent
C0~ absent
C02 present
C0£ absent
C02 present
0:2 ppm to give pH 9 .
1 ppm to give pH 9
2-3 parts per part of C02 to give pH 8-1
(corresponds to bicarbonate)
2-0 parts per part of C02 to give pH 7-4
1-4 parts per part of C02 to give pH 7
4 ppm to give pH 9
2-0 parts per part of
(corresponds to bicarbonate)
C02 to give pH 7-4
Source: Hamer et al. (1961).
It appears from current operating experience that the maintenance of pH 9
in the condensate is adequate to ensure that steam/water systems will be pro-
tected against corrosion.
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In estimating the overall requirements where part of the amine is re-
cycled, allowance must be made for losses in unrecovered steam and also to
some extent in blowdown. Sufficient amine must, therefore, be used not only
to deal with fresh carbon dioxide entering the system, but also to make good
those losses.
Filming amines—Certain straight-chain amines (containing 10 to 20 carbon
atoms) have been found useful for controlling corrosion in steam-condensing
systems in which the amines can form a protective adsorbed layer. This layer
acts as a barrier between the metal and any liquid water, thus protecting the
metal from attack by water containing dissolved oxygen or carbon dioxide.
Octadecylamine (synthetic stearylamine, C18H37NH2) is the material most com-
monly employed. Typically, the amine effects a reduction in corrosion of 80
to 95% with steam containing 4 to 60 ppm of carbon dioxide in the presence of
oxygen at boiler pressures in the range 100 to 600 lb/in2. It must be sup-
plied continuously to the steam, for the film does not appear to be very per-
sistent in operating conditions. The amine is either injected into the steam
lines or is pumped directly into the boiler where the amine distills off with
the steam. Feeding the amine directly to the boiler is reported to be inad-
visable because of the risk of thermal decomposition. The amine is stable,
however, to at least 425°C, and some authors have claimed stability at much
higher temperatures, e.g., 535°C and above (Fryling, 1966).
PRESENT STATUS OF USAGE OF AMINES IN BOILERS
From discussion with boiler experts, it became clear that the chemical
treatments currently employed with various types of boilers may differ from
the standard methods reported in the literature (Webb, 1978; Thiedke, 1978).
Therefore, the views and opinions of the sources consulted have been set forth
as reflecting the more current commercial practices.
Major neutralizing amines currently used to treat boiler feedwaters are
cyclohexylamine, morpholine, 2-diethylaminoethanol, and methylpropylamine
(Hollingshad, 1978), and ammonia. Benzylamines are frequently mentioned in
the literature as neutralizing amines for boilers, but Labine (1978) was not
aware of any such commercial use of benzylamines.
Filming amines used to treat boiler waters or steam condensate lines di-
rectly include octadecylamine and other fatty amines containing at least 12
carbon atoms. These may also include secondary amines. For example, Armak
Chemicals of Chicago produces the Ethomeen® series of secondary C12 to C18
amines that are sometimes used for boilers (Labine, 1978). The filming amines
tend to foul pumps and strainers and other parts of a boiler system, and their
popularity is declining (Hollingshad, 1978). However, if the neutralizing
secondary amines had to be replaced with other substances, Labine (1978) indi-
cated that filming amines would be used. Other experts believed that hydra-
zine and ammonia would be the more likely replacements for neutralizing
amines.
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The producers of boiler water additives usually formulate products with a
mixture of amines having different volatilities. If the system covers rela-
tively short distances, e.g., in a power plant where the boiler, turbine, and
condenser are in close proximity, the amines used do not need to be highly
volatile. In a refinery, where miles of piping may be employed, a product
volatile enough to carry to the end of the system is needed. By applying the
proper blend of high- and low-volatility amines, a product uniquely suited to
the particular boiler system's geometry can be provided (Hollingshad, 1978).
Several contacts, including Hertz (1978) of Nalco Chemical Company,
stated that nitrites are not normally added purposely to boilers. They are,
however, used in closed heating or cooling systems, possibly with amines'"
(Labine, 1978; Hollingshad, 1978; Gabrelli, 1978). Nitrites might come in
contact with boiler water because of some failure of a nitrite-containing
closed system incorporated within a boiler system (Hollingshad, 1978). Webb
(1978) stated that in modern-day power plant practice, the only possible use
of nitrites would be as "boron nitrite" in the closed cycle cooling water (in
place of sodium dichromate). Other industrial sources specified the use of
sodium nitrite plus a borate buffer; and it is likely that such a combination
is what Webb referred to as "boron nitrite."
Nitrates are also not intentionally added to boiler waters. They may
rarely be present because a water softener might have been recharged with ni-
tric acid (not a common practice) or because the plant is a meat plant
(Labine, 1978). Nitrates have been used in the past as part of the "boilout"
compound to clean down boilers as a precaution against caustic embrittlement
(Murphy, 1978), but this method is now considered obsolete.
MARKET INFORMATION
About six volatile amines are in general use as boiler water additives
(Hollingshad, 1978). These are listed below in Table 4-4 along with an esti-
mate of their current annual consumption in boiler water. Appendix D contains
available market information on these amines and related products obtained
from nonconfidential information submitted to EPA by manufacturers and import-
ers as of January 1979. A discussion of the overall market for amines as cor-
rosion inhibitors is presented in Appendix B.
Calgon, Nalco Chemical Company, and Betz Laboratories are the largest
suppliers of boiler water additives. Olin Water Services, Mogul Corporation,
Dearborn Chemical Division, Chemed Corporation, and Drew Chemical Corporation
are intermediate-sized companies; and there are a great many small companies.
The eight named companies, however, probably represent 90 to 99% of the market
for these materials (Hollingshad, 1978).
Boilers are considered open systems because of loss of steam or conden-
sate and the drainage of "blowdown," the periodic removal of concen-
trated solids in the boiler.
35
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TABLE 4-4. ESTIMATED CONSUMPTION OF SELECTED
AMINES AS BOILER WATER ADDITIVES
Estimated
1978 consumption
Type of amine (metric tons)
Neutralizing amines
Cyclohexylamine 3,200-3,600
Morpholine 1,800-2,200
2-Diethylaminoethanol 900-1,400
Methylpropylamine 400
All others " 200
Total 6,500-7,800
Filming amines
Octadecylamine 2,300
All others 200
Total 2,500
Sources: Stevens (1978) and MR! estimates.
About 40% of the total annual U.S. cyclohexylamine production is used for
pH adjustment in boiler systems. It is sold directly to water treatment firms
(Meek, 1978).
The total demand for morpholine in 1975 was about 11,000 metric tons.
About 2,700 metric tons were used in corrosion inhibitors (of this quantity,
1,800 to 2,200 metric tons were used as neutralizing amines in boiler water -
see Table 4-4); about 3,600 metric tons went into rubber chemicals; and about
900 metric tons went into each of the following categories: optical brighten-
ers, waxes and polishes, alkylmorpholines, miscellaneous, and exports (Mjos,
1978). Several volatile boiler water amines are permitted by the U.S. Food
and Drug Administration (FDA) to be "safely used in the preparation of steam
that will contact food" (Federal Register, 1977). According to the FDA, steam
in direct contact with food may contain less than or equal to 10 ppm cyclo-
hexylamine, less than or equal to 15 ppm 2-diethylaminoethanol, less than or
equal to 10 ppm morpholine, or less than or equal to 3 ppm octadecylamine (all
36
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of these with the proviso that the steam is not to contact milk and milk prod-
ucts) (Code of Federal Regulations, Part 121.1088, 1976).
Less than 4,000 metric tons of 2-diethylaminoethanol was produced in the
United States in 1976 (Mullins, 1978). 2-Diethylaminoethanol is also used in
the preparation of medicinals and antimalarials.
Methylpropylamine has only recently been used as a boiler water neutral-
izing amine (Stevens, 1978).
POTENTIAL. FOR NITROSAMINE FORMATION IN BOILERS
There is no experimental evidence to indicate whether or not nitrosamines
are formed in boilers as a result of the addition of boiler-water amines.
Most boilers are operated under conditions which would (a) limit the possibil-
ity for nitrosamine formation and (b) probably result in the destruction of
any nitrosamine that might be formed. However, under certain circumstances,
the possibility for nitrosamine formation is conceivable. These possibilities
are discussed below.
Modern High-Pressure Boilers
Nitrates and nitrites are potential nitrosating agents for boiler water
amines. However, neither nitrates nor nitrites are ordinarily added to boiler
water (Hollingshad, 1978). For some high-pressure boilers, such as those used
by electric utilities, high purity water is essential. As pointed out ear-
lier, purification procedures include the careful removal of dissolved solids,
including nitrates which occur in most untreated waters in the range 1 to 10
ppm. Some purification procedures require deionization of the water, and this
process would remove nitrate and nitrite (as well as other inorganic ions).
However, nitrosamines could possibly be introduced into water by resins used
for deionization; samples of deionized water have been found to contain as
high as 250 ng/liter of N-nitrosodimethylamine (Cohen and Bachman, 1978).
Other potential nitrosating agents are oxides of nitrogen from air. How-
ever, the presence of dissolved oxygen and carbon dioxide in boiler water is
undesirable; therefore, nearly complete deaeration of boiler water is ordinar-
ily employed. These procedures would be expected to reduce greatly the con-
centration of dissolved nitrogen oxides in the water.
A further detriment to the formation and stability of nitrosamines in
boilers is the fact that they are operated at high pH values, around pH 9 or
10. The classical secondary amine-nitrite reaction would not be expected to
occur at these pH values although the nitrosation of amines by oxides of ni-
trogen occurs rapidly at these pH values (see Appendix C).
Although there are limited data on the thermal degradation of nitrosa-
mines in water, most of them are known to be thermally unstable, especially at
temperatures in the range of 300°C. Temperatures of 250 to 300°C are attained
in high-pressure boilers and sustained for relatively long periods of time.
37
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Thus, eventual thermal decomposition of most nitrosamines would be expected
under these conditions. Furthermore, there is evidence that the thermal sta-
bility of some amines is greatly reduced at high pH values such as found in
boiler water (Lakings, 1980).
Medium-Pressure Boilers
Boilers operating in the pressure range of 100 to 500 psi (maximum tem-
perature about 240°C) utilize much different water treatment practices than
higher pressure boilers. This type of boiler commonly utilized a coordinated
phosphate treatment system to allow operation with zero-added caustic or to
maintain the desired pH with very minor caustic additions. Sodium sulfite (or
in some cases hydrazine) may be used as an oxygen scavenger. Since the intro-
duction of welded boiler construction (about 1930) and stress relief of the
boiler parts before use, caustic embrittlement has become virtually a problem
of the past. The practice of using sodium nitrate (at 200 to 400 ppm) to pre-
vent caustic embrittlement is unknown to all the boiler specialists who were
consulted in this study.
Hence, the occurrence of nitrosamines in moderate-pressure boilers is not
likely to be attributable to reactions between organic amines and other chemi-
cals intentionally added to manage these boiler water systems.
Low-Pressure Boilers
There are hundreds of thousands of relatively small, low-pressure boilers
(25 to 200 psi, maximum temperature less than 190°C) in use for heating and
process steam generation. The majority of these boilers are treated inter-
nally by the use of proprietary boiler water additives, which typically con-
tain phosphates, sodium sulfite, and a sludge-conditioning polymer. The oc-
currence of caustic embrittlement is so rare that none of the boiler compound
suppliers were aware of any additives which presently contain nitrates or ni-
trites. However, they cautioned that some boiler additives formulated by some
of the numerous, small boiler treatment supply firms could still incorporate
nitrates and/or nitrites. The water used as feed presents another possible
source of nitrite. Hence, the possibility of reaction between neutralizing
amines and nitrates or nitrites is at least possible in some low-pressure
boiler systems.
Hot-Water Boilers
So-called "hot-water boilers," used to circulate water to about 77°C for
heating or to generate low-pressure steam at 10 to 12 psi with 100% condensate
return, may employ sodium nitrite as a corrosion inhibitor. These systems are
closed and require no makeup water since losses occur only if leaks are pres-
ent. Chromate corrosion inhibitors are commonly used, but a combination of
sodium nitrite and borate buffer is also widely employed. The water circulat-
ing systems do not use neutralizing or film-forming amines since the proper pH
is maintained by the buffer system. The development of nitrosamines in hot-
water heating systems is regarded as extremely unlikely.
38
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Reports of Nitrosamines in Steam Emissions from Boilers
A recent survey of N-nitroso compounds observed that small amounts (0.002
Hg/g) °f N-nitrosomorpholine were found in the steam condensate from boilers
at a B. F. Goodrich plant which produces chemicals for the rubber industry
(Fan, Fajen, and Rounbehler, 1978). The authors were unable to ascertain ex-
actly how this nitrosamine (or other nitrosamines detected at the plant) was
formed. In the report, they speculated that it was most likely formed by the
transnitrosation reaction of morpholine with N-nitrosodiphenylamine. The lat-
ter compound, a vulcanization retarder, is produced at this plant and was de-
tected at various locations within the plant in amounts ranging from 47 to
50,000 (Jg/g in bulk samples and from 0.3 to 47 |Jg/m3 in air samples.
Morpholine is used at this plant as a starting material for the manufac-
ture of bismorpholine carbamylsulfenamide, an accelerator. The N-nitrosomor-
pholine was detected at various locations throughout the plant, ranging from
0.002 (Jg/g in steam condensate to 731 (Jg/g in scrappings from staircases, and
from 0.07 to 6.8 |Jg/m3 of the compound in air samples. The authors also ob-
served that this compound exists as a contaminant in morpholine (0.8 (Jg/g) and
this fact may account for its presence in the samples taken.
Fajen (1979) of NIOSH provided additional information concerning these
studies. Morpholine was also used as a neutralizing amine for the boilers at
the B. F. Goodrich plant. Many of the steam lines at the plant were leaking,
and these leaks were the source of their samples. The program team was con-
cerned that the steam emissions might contain N-nitrosomorpholine as a result
of the known contamination of the morpholine starting material. However, this
was subsequently shown to be unlikely because it was not detected in the steam
emissions from boilers at other plants which used morpholine as a neutralizing
amine.
As part of this program, 28 different plants were visited for the purpose
of detecting N-nitrosamine contamination. Steam condensate samples were ex-
amined only when nitrosamines were detected elsewhere in the plants. No sam-
ples of boiler blowdown were taken at any of the plants, and no record was
made of the operating characteristics of the boilers. The foremen of the
boiler rooms were contacted in order to determine whether morpholine was used
as a boiler additive. Bulk samples of the boiler additives were also taken
for analysis for the presence of morpholine and N-nitrosomorpholine. Some of
the plants used morpholine; for example, five plants serving the rubber indus-
try used morpholine in the boilers. However, of all the plants visited, only
the B. F. Goodrich plant was found to contain this nitroso compound in the
steam condensate from boilers.
At the present time, it is not possible to rule out morpholine in the
boiler as a source of N-nitrosomorpholine contamination. However, nitrosamine
formation via a transnitrosation reaction outside of the boiler appears to be
the most likely mechanism. Transnitrosation can only occur when other nitro-
samine contaminants are present.
39
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Additional studies are required to clarify this situation; additional
steam condensates from boilers using morpholine (and other amines) should be
examined using sampling techniques which would preclude transnitrosation.
Also, similar examinations should be made of boiler blowdown.
40
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Stevens, J. 1978. Boiler Water Product Manager, Calgon Corporation.
Pittsburgh, Pennsylvania. Personal communication to A. Meiners, August 15.
Stroud, E. C., and W. H. J. Vernon. 1952. The Prevention of Corrosion in
Packaging. III. Vapor Phase Inhibitors. Journal of Applied Chemistry 2:178-
184.
Swift, C. 1978. American Hoechst Corporation. Elk Grove Village, Illinois.
Personal communication to B. Carson, August 8.
Takahashi, K. 1975. Volatile Corrosion Inhibitors. Boshaku Gijutsu 24(9):
479-489.
Thiedke, J. 1978. Western Chemical Company, Kansas City, Missouri. Personal
communication to Howard Gadberry.
Trabanelli, G., A. Fiegna, and V. Carassiti. 1967. Relations Between Struc-
ture and Inhibitor Efficiency in the Vapor Phase. Centre Beige Etude
et Doc. Eaux et Air. Tribune du Cebedeau (Liege). 20(288):460-466.
Trabanelli, G., and F. Zucchi. 1976. Fundamentals of Inhibition with VCI's.
Proc. Nat. Assoc. Corrosion Eng. Conf. Houston, Texas. March 22-26.
Paper No. 82.
Uhlig, H. 1971. Corrosion and Corrosion Control. 2nd Ed., John Wiley, New York.
pp. 270-282.
Van Sice, L. 1978. Customer Relations Representative, Eastman Kodak Company,
Eastman Organic Chemicals. Rochester, New York. Personal communication
to B. Carson, August 1.
Van Winkle, H. 1978. Sales Manager, VCI Paper, Daubert Chemical Company.
Hinsdale, Illinois. Personal communication to H. Owens, July 31.
44
-------
Wachter, A., and N. Stillman. 1952. Corrosion Inhibition with a Mixture
of Inhibitors of Differing Volatility. U.S. Patent No. 2,577,219.
Wachter, A., T. Skei, and N. Stillman. 1951. Dicyclohexylammonium Nitrite,
a Volatile Inhibitor for Corrosion Preventive Packaging. Proc. Nat. Assoc.
Corrosion Eng. Conf. Houston, Texas, pp. 284-294.
Walters, N. 1978. Anderson-Stolz Corporation. Kansas City, Missouri. Personal
communication to H. Gadberry, August 15.
Webb, L. 1978. Chief of the Water Chemistry Section, Black and Veatch Engi-
neers. Kansas City, Missouri. Personal communication to H. Gadberry,
August 11.
Woodward, E. R. 1958. Treating Industrial Water with Hydrazine. In: Proc.
Internat. Conf., Bournemouth, England, May 1957. Whiffen and Sons, London.
pp. 98-110.
Zisman, W. A., D. R. Spessard, and J. G. O'Rear. 1951. Noninflammable Hy-
draulic Fluids and Lubricants. U.S. Patent No. 2,558,030. June 26.
-------
APPENDIX A
PHYSICAL PROPERTIES OF VCIs. BOILER WATER
AMINES AND RELATED COMPOUNDS^/
a/ Unless otherwise noted, the physical properties of these compounds were
obtained from the Merck Index (9th Edition, 1976, published by Merck
and Company, Inc., Rahway, New Jersey) or the Dictionary of Organic
Compounds (4th Edition, 1965, published by Oxford University.Press,
New York).
47
-------
CONTENTS
Benzotriazole 49
Cyclohexylamine 50
Cyclohexylammonium Carbonate 51
Dicyclohexylamine • • • • 52
Dicyclohexylammonium Nitrite 53
Diethanolamine 54
2-Diethylaminoethanol 55
Diisopropylamine 56
Diisopropylammonium Nitrite 57
N-Ethylmorpholine 58
Mercaptobenzothiazole 59
Methylpropylamine 60
Morpholine. 61
Naphthylamine 62
N-Nitrosodibutylaraine 63
N-Nitrosodicyclohexylamine 64
N-Nitrosodiisopropylamine 65
N-Nitrosodimethylamine .66
N-Nitrosodiphenylamine. 67
N-Nitrosomethylpropylamine 68
N-Nitrosomorpholine 69
Octadecylamine 70
Tolyltriazole 71
Triethanolamine 72
48
-------
BENZOTRIAZOLE
Chemical Formula: C,H N
653
H
.1
Structure:
PLJ
Molecular Weight: 119.12
Description: White powder
Melting Point: 98.5°C
Boiling Point: bp. = 204 C; bp0 n = 159°C
15 . i *0
100
Density: d = 1.19
Solubility: Soluble in alcohol, toluene, chloroform, DMF.
Slightly soluble in water.
Source: Sherwin-Williams (1976)
49
-------
CYCLOHEXYLAMINE
Chemical Formula: C,H,-N
o U
Structure: /\ NH
W" 2
Molecular Weight: 99.17
Description: Liquid, strong fishy amine odori
Melting Point: solidifies at -17.7°C
Boiling Point: bp_,n = 134.5°C
7oU
25
Density: d = 0.8647
25
Refractive Index: n = 1.4565
Solubility: Completely miscible with water and common organic
solvents.
50
-------
CYCLOHEXYLAMMONIUM CARBONATE
Chemical Formula: c H..N 0
13 26 i
\ V~NHC02 iH3N \ /
Structure
Molecular Weight: 242.36
Description: White crystals.
Vapor Pressure: 0.394 mm Hg at 25°C
Solubility: Soluble in water, methanol and ethanol.
Source: Stroud and Vernon (1952).
51
-------
PICYCLOHEXYLAMINE
Chemical Formula: C H N
Structure:
Molecular Weight: 181.31
Description: Liquid, faint fishy odor
Melting Point: solidifies at -0.1°C, mp ~ 20°C
Boiling Point: bp_,.n = 256°C
7oU
Flash Point: 110°C
Density: d 5 = 0.9104
25
Refractive Index: n = 1.4823
Solubility: Slightly soluble in water; soluble in organic solvents
52
-------
DICYCLOHEXYLAMMONIUM NITRITE (DICHAN)
Chemical Formula: C H N 0
Structure: \...y ^>NH NO
Molecular Weight: 228.33
Description: White crystalline solid
Melting Point: 173 to 180°C
154°C (technical product)
Vapor Pressure: 1.2 x 10* mm Hg at 21.0°C
Solubility: Slightly soluble in water; soluble in methanol,
ethanol
Sources: Wachter et al. (1951); Wolfe and Temple (1948).
53
-------
DIETHANOIAMINE
Chemical Formula: C^H11N02
Structure: (HOCH2CH2)2NH
Molecular Weight; 105.14
Boiling Point: bp760 = 268.8°C
Melting Point: mp = 28°C
Flash Point: 300°F
?n
Density: d£ = 1.09664
Dipole Moment: 2.81
Viscosity: V30 = 351.9 cp
Solubility: miscible with water, methanol, acetone, very soluble
in ethanol, slightly soluble in benzene,, ether.
Source: Weast (1976) and Toxicology Data Bank File.
54
-------
2-DIETHYLAMINOETHANOL
Chemical Formula: C^H.-NO
D 15
Structure: ^>N-CH CH OH
C2H5
Molecular Weight: 117.19
Description: Liquid
Boiling Point: bp_,- = 163°C
7oU
25
Density: d = 0.8800
25
Refractive Index: n = 1.4389
Solubility: Soluble in water, alcohol, ether, benzene,
55
-------
DIISOPROFYLAMINE
Chemical Formula: C.H, _N
o 15
GH
Structure: 3
CH3
Molecular Weight: 101.19
/
Description: Liquid, characteristic odor, strongly alkaline
°
Boiling Point: 84 G
22
Density: d = 0.722
Solubility: Soluble in water, alcohol
56
-------
DIISOPROPYLAMMONIUM NITRITE (DIPAN)
Chemical Formula: C^H, ,0 N
o lo z i
Structure: 3 /^ N°2
Molecular Weight: 148
Melting Point: 136 to 137°G
Vapor Pressure: 0.012 ram Hg at 20°C
Sources: Wolfe and Temple (1948); Putilova et al. (1960),
57
-------
N-ETHYIMORPHOLINE
Chemical Formula:
Structure: 0 N -
Molecular Weight: 115.18
Boiling Point: bp763 = 138-139°C
Freezing Point: fp = 32 °C
Melting Point: rap = -63 °C
Solubility: Soluble in water, alcohol, ether, acetone, benzene.
Source: Toxicology Data Bank File.
58
-------
MERCAPTOBENZOTHIAZOLE
Chemical Formula: CyH5NS
Structure: |( )l *- SH
Molecular Weight: 167.25
Density: d25 = 1.42
Melting Point: mp = 180.2 - 181.7
Solubility: Solubility at 25° (g/100 ml) in alcohol: 2.0;
ether: 1.0; acetone: 10.0; benzene: 1.0;
soluble in alkalies and alkali carbonate
solutions.
59
-------
METHYLPROPYLAMINE
Chemical Formula: C,H, ,N
4 11
Structure: CH CH CH NHCH
J £m £- J
Molecular Weight: 73
Description: Liquid with fishy odor
Boiling Point: 62 to 64°G
Density: d17 = 0.7204
Solubility: Soluble in water
60
-------
MORPHOLINE
Chemical Formula: C. HJMO
4 9
/ \
Structure: 0 NH
Molecular Weight: 87.12
Description: Colorless hygroscopic liquid, with characteristic
amine odor*
Melting Point: -4.9°C
Boiling Point: bp_,,n = 128.9°C; bpf = 20.0°C
7oU o
Flash Point: 38°C
20
Density: d = 0.994
20
Vapor Density: d, = 1.007
Vapor Pressure: 7.0 mm Hg at 20° C
20
Refractive Index: n = 1.4540
Solubility: Miscible with water, acetone, benzene, ether, castor
oil, methanol, ethanol, ethylene, and glycol.
Source: Mjos (1978),
61
-------
NAPHTHYLAMINE§-/
Chemical Formula: CRN
10 9
Structure:
Molecular Weight: 143.19
Boiling Point:
a.
- 300.8°C
-.306.1'C
Melting Point:
mp = 50°C
mp = 113° C
Density:
= 1.1229
d98 = 1.0614
4
Solubility:
Soluble in 590 parts
water, freely solu-
ble in alcohol and
ether.
Soluble in hot water,
alcohol, ether.
Source: Weast (1976).
a/ The International Agency for Research on Cancer has published an evalua-
tion of the carcinogenicity of 1-naphthylamine (a) and 2-naphthylamine
(3): "Epidemiological studies have shown that occupational exposure
to 2-naphthylamine, either alone or when present as an impurity in other
compounds, is strongly associated with the occurrence of bladder cancer.
There is no doubt that 2-naphthylamine is a human bladder carcinogen."
(IARC, 1973.)
"Exposure to commercial 1-naphthylamine containing 4-10% 2-naphthylamine
is strongly associated with bladder cancer. It is not possible on pres-
ent evidence to decide whether 1-naphthylamine free of the 2-isomer is
carcinogenic to man." (IARC, 1973.)
62
-------
N-NITROSODIBUTYLAMINE -
Chemical Formula: CHH10N_0
o 18 L
^^CH^—CH — CH^—CH~
Structure: 0 =' N - N
Molecular Weight: 158.28
Description: Pale yellow liquid
Boiling Point: bp?60 = 234° - 237°C
Density: d20 = 9.009
Solubility: 12% soluble in water at room temperature, miscible
with hexane, dichloromethane, and other organic
solvents.
Source: MRI, (1977).
a/ The International Agency for Research on Cancer has published an evalua-
tion of the carcinogenicity of N-nitrosodibutylamine: "There is suf-
ficient evidence of a carcinogenic effect of N-nitrosodi-n-butylamine
in several experimental animal species. Although no epidemiological
data were available, N-nitrosodi-n-butylamine should be regarded for
practical purposes as if it were carcinogenic to humans." (IARC, 1978.)
63
-------
N-NITROSODICYCLOHEXYLAMINE
Chemical Formula: C.-H^ISL
12 22 2
Structure:
Molecular Weight: 210.36
Description: Crystalline needles
Melting Point: 107°C
Solubility: Water solubility 0.0015 g/100 ml
Source: Druckrey et al. (1967)j Wolfe and Temple (1948)
64
-------
N-NITROSODIISOPROPYLAMINE
Chemical Formula: C.FL.N.O
6 14 2
Structure: 3 N-NO
Molecular Weight: 130.22
Boiling Point: 96°C at 28 mm Hg
Solubility: Water solubility, 1.3 g/100m^
Source: Druckrey et al. (1967).
65
-------
N-NITROSODIMETHYLAMINE -
Chemical Formula:
Structure: H3C
- NO
Molecular Weight: 74.09
Boiling Point: bp,cr. = 154°C
/oU
20
Density: d = 1.0048
Refractive Index: n = 1.4368
Solubility: Miscible with water, methylene chloride, vegetable
oils; soluble in all common organic solvents and
in lipids; very soluble in alcohol, ether.
Source: Toxicology Data Bank File.
a_/ The International Agency for Research on Cancer has published an evaluation
of the carcinogenicity of N-nitrosodimethylamine: "There is sufficient
evidence of a carcinogenic effect of N-nitrosodimethylamine in many ex-
perimental animal species. Similarities in its metabolism by human and
rodent tissues have been demonstrated. Although no epidemiological data
were available, N-nitrosodimethylamine should be regarded for practical
purposes as if it were carcinogenic to humans." (IARC, 1978.)
66
-------
N-NITROSODIPHENYLAMINE
Chemical Formula:
Structure:
\x_ _y /
t
N
0
Molecular Weight: 198
Description: dark-brown solid
Melting Point: 63 - 66°C
Solubility: Soluble in warm EtOH, Warm
Source: NCI, 1979.
67
-------
N-NITROSOMETHYLPROPYLAMINE
Chemical Formula: C.H,rtONL
4 10 2
Structure: CH.CH.CH^
3 2 S-NO
Molecular Weight: 102
Boiling Point: 175°C
68
-------
N-NITROSOMORPHOLINES/
Chemical Formula: C H N 0
M- o i 2.
Structure: o N-NO
Molecular Weight: 116.1
Description: Yellow Crystals
Melting Point: 29°C
Boiling Point: bp y^7 = 224-225°C
bp6 = 96°C
Solubility: Miscible in water; soluble in organic solvents
Source: IARC (1978).
_a/ The International Agency for Research on Cancer has published an evalua-
tion of the carcinogenicity of N-nitrosomorpholine: "There is sufficient
evidence for a carcinogenic effect of N-nitrosomorpholine in several
experimental animal species. Although no epidemiclogical data were
available, N-nitrosomorpholine should be regarded for practical pur-
poses as if it were carcinogenic to humans." IARC (1978).
69
-------
OCTADECYLAMINE
Chemical Formula: C H NH
lo J7 2
Structure: CH
j z j./
Molecular Weight: 269
Description: Liquid
Boiling Point: bp0 _ = 172 to 173°G
2. »j
70
-------
TOLYLTRIAZOLE
Chemical Formula: G7H7No
Structure:
Molecular Weight: 133.16
Description: off-white granules
Density: d = 1.13
Solubility: Slightly soluble in water; soluble in methanol and
other alcohols.
Source: Sherwin-Williams (1976).
71
-------
TRIETHANOLAMINE
Chemical Formula:
Structure:
Molecular Weight: 149.19
Boiling Point: bp76Q = 335. 4°C
Density: d u = 1.1242
4
Flash Point: 365°F
Melting Point: mp = 21,2°C
20
Refractive Index: n'" = 1.4852
Viscosity: V25 = 590.5 cp
Source: Weast. (1976).
72
-------
APPENDIX A - REFERENCES
Druckrey, H., R. Preussmann, S. Ivankovik and D. Schmahl. 1967. Organotrope
Carcinogene Wirkungen bei 65 Verschiedenen N-Nitroso-Verbindungen an BD-
Ratten. Zeitschrift fur Krebsforschung 69:103-201.
IARC. 1973. International Agency for Research on Cancer. IARC Monographs
on the Evaluation of the Carcinogenic Risk of Chemicals to Man: Some
Aromatic Amines, Hydrazine and Related Substances, N-nitroso Compounds and
Miscellaneous Alkylating Agents. Volume 4. International Agency for
Research on Cancer, Lyon, France, p. 93, 107.
IARC. 1978. International Agency for Research on Cancer. IARC Monographs on
the Evaluation of the Carcinogenic Risk of Chemicals to Humans: Some N-
Nitroso Compounds. International Agency for Research on Cancer, Lyon,
France, p. 67, 152, 275.
Mjos, K. 1978. Cyclic Amines. Encyclopedia of Chemical Technology, Kirk-
Othmer. 3rd ed. Volume 2. p. 295.
MRI, Midwest Research Institute. 1977. Draft Report, Carcinogen Safety
Monograph No. 2, Six Selected N-Nitrosamines. NCI Contract No. N01-CO-
65331. p. 6 & 7.
NCI, National Cancer Institute. 1979. Bioassay of N-Nitrosodiphenylamine
for Possible Carcinogenic!ty. NIH Publication No. 79-1720. U.S. Department
of Health, Education, and Welfare, p. 3.
Putilova, I. N., S. A. Balexin, and V. P. Barannik. 1960. Metallic Corro-
sion Inhibitors. Pergamon Press, New York, New York. p. 161-165.
Sherwin-Williams Company. 1976. COBRATEC - Corrosion Inhibitors for Copper,
Brass, Bronze, and Multi-Metal Systems. Technical Bulletin 531.
Stroud, E. C., and W. H. J. Vernon. 1952. The Prevention of Corrosion in
Packaging. III. Vapor Phase Inhibitors. Journal of Applied Chemistry
2:178-184.
TDB, Toxicology Data Bank. National Library of Medicine.
Wachter, A., T. Skei, and N. Stillman. 1951. Dicyclohexylammonium Nitrite,
a volatile Inhibitor for Corrosion Preventive Packaging. Proceedings of
the National Association of Corrosion Engineers Conference. Houston, Texas.
pp. 284-294.
Weast, R. C. 1976. Handbook of Chemistry and Physics. Chemical Rubber
Publishing Co. Cleveland, Ohio.
Wolfe, J. K. and K. L. Temple. 1948. The Preparation of Nitrite Salts of
Alkyl Amines. J. Amer. Chem. Soc. 70:1414-1416.
73
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APPENDIX B
THE MARKET FOR AMINES AS CORROSION INHIBITORS
A recent report by Frost and Sullivan entitled The Corrosion Inhibitors
Market estimated that 1976 expenditures for corrosion control goods and ser-
vices were $10.5 billion (Anonymous, 1978a). Three classes of corrosion
inhibitors were considered. The water-soluble inhibitors market in 1976
was said to be $204 million; the oil-soluble inhibitors market, $92 million;
and the vapor phase inhibitors market, $16.3 million.
A 1975 survey by the National Association of Corrosion Engineers
(NACE, 1976) estimated that total expenditures for corrosion control were
$9.7 billion and vapor phase inhibitor purchases were $12.4 million.
The NACE survey queried its membership about the amounts spent for
corrosion protection, including the chemical inhibitors divided into the
categories: water-soluble, oil-soluble, and "vapor phase" inhibitors.
Table B-l presents the survey's results for the latter category.
Miksic (1978), Chairman of the NACE task committee on volatile cor-
rosion inhibitors (T-3A-4), suspected that in most cases, boiler-water
chemicals, not VCIs, are what the NACE membership perceives as "corrosion
inhibitors, vapor phase type" (Table B-l). Miksic recognizes that a seman-
tics problem exists and is attempting to clarify the definition of these
corrosion inhibitors within NACE.
Attempts were made to obtain the types and quantities of the compounds
used as indicated in Table B-l with emphasis on obtaining data from indus-
tries which appear to use over 78% of the vapor phase inhibitors, i.e.,
the chemical and petrochemical industries, and the petroleum production
and refining industries. The author of the NACE report was contacted
(Castleberry, 1979) but could not provide these data and believed that
they were not available.
The Charles H. Kline and Company, Inc., of Fairfield, New Jersey, will
soon publish a multiclient study entitled "Refinery, Gas Conditioning, and
Pipeline Chemicals, 1978." According to a Kline representative (Rosenberg,
1979), this 2-1/2 year survey will include information on chemical composi-
tions, quantities, market share, dollar volume, typical usage, and market
forecasts. The survey will include refinery boiler water chemicals and
corrosion inhibitors used in pipelines. According to the company's brochure
(Kline, 1979), most of the information in the survey appears to deal with
dollar volumes, not pounds, of chemicals, and categories of products, not
specific compounds; the only specific compounds pertinent to this study
that were noted in an outline of this study are morpholine, monoethanolamine,
75
-------
TABLE B-l. ESTIMATED USE OF VAPOR PHASE CORROSION
INHIBITORS BY INDUSTRY
Amount spent on "corrosion
inhibitors, vapor phase types"
Industry
Chemical and petrochemical industries
Petroleum production
Petroleum refining
Electrical utilities
Engineering and/or construction
Crude oil pipeline transmission
Natural gas transmission
Pulp and paper industry
Government
Research
Metals industry
Nuclear power industry
Equipment manufacturing industries
Gas utilities
Water utilities
Communications
Other industries
Dollars
(millions)
4.012
3.199
2.482
0.396
0.281
0.263
0.237
0.208
0.158
0.114
0.105
0.079
0.057
0.003
0.000
0.000
0.789
12.383
a/
Percentr-
32.4
25.8
20.0
3.2
2.3
2.1
1.9
1.7
1.3
0.9
. 0.8
0.6
0.5
0.0
0.0
0.0
6.4
a./ Figures may not total 100% due to rounding.
Source: NACE, 1976.
76
-------
and diethanolamine; of these, only morpholine is used extensively as a
boiler water additive. The absence of other volatile amines from the
outline confirms our opinion that the "vapor phase types" of corrosion
inhibitors listed by NACE (Table B-l) as used by the "petroleum refining,"
"natural gas transmission," and "crude oil pipeline transmission" indus-
tries are indeed boiler water additives, and not VCIs.
A partial summary of the information compiled by Kline and Company
is presented in Table B-2.
A comparison of the estimates made by Kline and by NACE shows some
important discrepancies (Table B-3). As indicated in the table, major
differences occur in estimates of the amounts of corrosion inhibitors
used: (a) to treat water in refinery operations and (b) in petroleum and
gas transmission operations.
Perhaps the major reason for these discrepancies is that each estimate
was based to a large extent upon personal knowledge and opinion obtained
via interviews. Another problem is the fact that boiler water amines are
commonly sold to the user at a price which includes in-plant corrosion .
control service (Ward, 1979).
The size of the discrepancies in dollar volume obtained in these two
extensive and detailed surveys provides an indication of how time-consuming
and difficult it would be to obtain reliable information concerning the
quantities and types of chemicals used. Rosenberg (1979), who is participat-
ing in the Kline and Company survey, estimated that a minimum of 200 inter-
views, including some on-site visits, would be required in order to obtain
even a rough estimate of the chemicals used and their amounts. He also
stated that the end users of the inhibitors would not be very helpful
mainly because they do not know the composition of the products they use.
Frost and Sullivan, Inc., New York, New York, published a report
in 1978 entitled "Corrosion Inhibitors Market." According to their cata-
log, this report provides a forecast of the corrosion inhibitor market,
including markets for boilers, oil well, and refinery operations. In this
report, as well as the Kline and Company survey, the emphasis appears to
be placed on dollar amounts of products sold and not pounds of chemicals
used.
Personal Interviews
Knowledgeable representatives of the following chemical and petro-
chemical industries were contacted concerning volatile amines used as cor-
rosion inhibitors.
77
-------
TABLE B-2. ESTIMATED U.S. SALES OF CHEMICALS AND
FORMULATED CHEMICAL SPECIALITIES IN
REFINING, GAS CONDITIONING, AND
PIPELINE TRANSMISSION, 19771/
Use category
Millions of dollars
Refining
Water treatment
Corrosion inhibitors
Other chemical products
Processing
Corrosion inhibitors
Other chemical products
Gas conditioning
Ethanolamines
Other chemical products
$ 30
52
82
15
16
Total $113
$ 30
Total $ 57
Pipeline transmission
Petroleum
Corrosion inhibitors
Other chemical products
Gas
Corrosion inhibitors
All other
Total
Grand total
$ 15
18
$ 33
$ 15
2
$ 17
$ 50
$220
Source: Kline (1979)
a/ Excludes service.
78
-------
TABLE B-3. COMPARISON OF NACE AND KLINE SURVEYS CONCERNING CORROSION
INHIBITORS (MILLIONS OF DOLLARS)
Kline estimate
(for 1977)
NACE estimate
(for 1975)
Refining
Water treatment
Processing
Pipeline transmission
Total
30
11
45
2.4 ("vapor phase types")
"32
Petroleum
Gas
15
15
Total 30
9.4 (0.26 "vapor phase types")
4.9 (0.24 "vapor phase types")
14.3
Sources:. Kline (1979); NACE (1976).
y-
*
*
*
*
Union Carbide, Tarrytown, New York
Du Pont, Wilmington, Delaware
Dow Chemical, Midland, Michigan
Standard Oil Company, Sugar Creek, Missouri
Amoco Research, Naperville, Illinois
Shell Oil Company, Houston, Texas
Gulf Oil Company, Houston, Texas
Texaco, Inc., White Plains, New York
In general, these representatives know of no large-scale uses by their
industry group of volatile amines as corrosion inhibitors except in boiler
operations. They also were not knowledgeable of exactly what compounds were
contained in the boiler water chemicals, other than that they were neutral-
izing or film-forming amines.
79
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APPENDIX B - REFERENCES
Anonymous. 1978a. Corrosion. Inhibitor Market Expected to Double to $24 Bil-
lion by Year 1985. Chemical Marketing Reporter. 213(8). February 20. pp.
5, 21.
Castleberry, J. 1979. Author, National Association of Corrosion Engineers
NACE) Survey, 1976. Personal Communication to Ms. M. Simister. May 24.
Kline. 1979. Refinery, Gas Conditioning, and Pipelines Chemicals 1978.
Charles H. Kline & Co., Inc., Fairfield, New Jersey.
Miksic, B. A. 1978. President, The Cortec Corporation. St. Paul, Minnesota.
Personal communication to A. Meiners, July 13.
NACE. 1976. National Association of Corrosion Engineers. Corrosion - A
Devastating Problem that is Costing U.S. Industries $Billions Each Year.
Houston, Texas.
Rosenberg, L., 1979. Project Manager, Charles H. Kline & Co., Inc. Fairfield,
New Jersey. Personal communication to Ms. Mary Simister, May 24.
Ward, ¥. 1979. Director of Technology, Olin Water Services Division, Olin
Corporation, Overland Park, Kansas. Personal communication to A. F. Meiners,
August 14.
80
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APPENDIX C
REVIEW OF POSSIBLE NITROSAMINE FORMATION REACTIONS
OF VCIs AND BOILER WATER AMINES
The most likely possibility as a source of nitrosamines from VCIs
and boiler water amines is the nitrosation of secondary amines. All of
the VCI amines presently used are secondary amines, and about one-third
of the neutralizing amines are secondary amines. However, cyclohexylamine
and octadecylamine are primary amines which represent major fractions of
the market for neutralizing and filming amines, respectively (see text,
p. 34). In addition, 2-diethylamirioethanol is a tertiary amine which rep-
resents 10 to 20% of the market for neutralizing amines (see text, p. 34).
Edwards et al. (1978) have reported that "contrary to popular belief,
not only secondary amines, but also primary and tertiary amines can all
yield IJ-nitroso compounds."
Discussed below are the reactions which could produce nitrosamines
from VCIs and boiler water amines.
Nitrosation of Secondary Amines
The classic method for producing nitrosamines is the interaction of
secondary amines with nitrous acid; in practice, the method consists of
acidifying a solution containing a nitrite salt and. a secondary amine
(Mirvish, 1975).
RRNH + N0~ + H - > RN-NO + H0
In the acid-catalyzed nitrosation of secondary amines, nitrite is
usually first converted to nitrous acid, which in turn is converted to an
active nitrosating species: nitrogen (III) oxide (^O-j) , nitrous acidium ion
(H2N02+), nitrosyl cation (NO1), nitrosyl thiocyanate (ON-NCS ), or nitrosyl
halide (NOX ) (Olajos and Coulston, 1978). The nitrogen (III) oxide moiety
(N203 ^ > NOo'NO') is the active nitrosating agent in the pH range 1 to 4;
at the dilute acidic conditions that are encountered in the environment,
this moiety is likely the one which nitrosates secondary amines (Fine,
1979).
The N-nitrosation of secondary amines is usually very slow at neutral
or alkaline pH because of the low equilibrium concentration of nitrous an-
hydride. However, in the presence of formaldehyde, chloral (Keefer and
Roller, 1973), or some metal ions, appreciable nitrosation can occur even
at pH 6 to 11 (Fine, 1979).
81
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In pure buffered aqueous systems, dimethylamine in the presence of
nitrite was not nitrosated at pH values above 5»0j however, in sterilized
soil and sewage samples, nitrosation was observed to occur at pH values as
high as 7.7 (Mills and Alexander, 1976).
Nitrosation can take place by other reactions; for example dimethyl-
and diethyl-nitrosamines are evidently formed in air by the reaction of
nitrogen oxides with the secondary amines (Fine and Rounbehler, 1976).
The nitrosating agent can be nitrogen (II) oxide (NO), nitrogen (IV)
oxide (NO' .N20 ), or nitrogen (III) oxide (N20 ), (Edwards et al.,
1978). Nitrogen "(II) oxide (NO) itself has been shown to be a poor
nitrosating agent (Challis and Kyrtopoulos, 1976). However, nitrosation
in the presence of NO and air proceeds readily, presumably because of
oxidation of some of the NO to N02 and the formation of NjO^ from NO
and N0_. Nitrosation by N20 and N_0, proceeds rapidly at room tempera-
ture in aqueous solution at a pH in the range of 6 to 14. The reactions
are very much faster than those with acidified nitrite (Challis et al.,
Pitts et al. (1978) have reported studies of the nitrosation of diethyl-
amine in air containing ambient levels of NO and N02« Diethylatnine is rap-
idly nitrosated in the dark but is subsequently destroyed by sunlight.
Fan et al. (1978) have recently shown that certain C-nitro compounds-
can readily nitrosate secondary amines to form N-nitroso compounds. C-nitro
compounds are widely used as pesticides, bactericides, coloring agents,
drugs, and perfumes (Fine, 1979). The reaction occurs rapidly at neutral
and alkaline pHs, but alkaline conditions are the most favorable (Fine,
personal communication, 1978).
Transnitrosation of aliphatic secondary amines has also been demon-
strated to occur (Singer et al., 1978). Transnitrosation is the transfer
of the nitroso group of one N-nitrosamine to another amine to form a dif-
ferent N-nitrosamine.
R^N-NO + R3R4NH2 -> R R^N-NO +
Many transnitrosation reactions are known to take place in strong aqueous
acid (pH 1.5) and the reactions are catalyzed by nucleophiles such as thio-
cyanate or halide ion. Some secondary amines are more easily nitrosated by
this reaction than others; for example, morpholine can apparently be readily
nitrosated by a variety of nitrosamines (Fine, 1978). Also, some nitrosa-
mines appear to be stronger nitrosating agents than others (Singer et al.,
1978).
a/ A C-nitro compound is a compound in which a nitro group (N02 ) is
attached to an aliphatic carbon atom.
82
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The nitrosation of secondary amines by microorganisms at pH values
above 5.0 has been reported by several investigators (Archer et al., 1978).
Rate enhancements of from 12- to 49-fold have been observed when dihexylamine
was nitrosated at pH 3.5 in the presence of bacteria and yeast cells; a non-
enzymatic mechanism is proposed (Archer et al., 1978).
Very little has been reported concerning the potential transformation
to nitrosamines of secondary amines used as VCIs or boiler water additives.
N-nitrosomorpholine has been detected on one occasion in the steam emissions
from boilers (see text, p. 36). However, the morpholine added to the boiler
is not believed to be the source of the nitrosamine. Dichan, the nitrite
salt of a secondary amine, apparently can be at least partially transformed
to the corresponding nitrosamine (see text, p. 21).
Nitrosamines from Primary and Tertiary Amines
Although the nitrosation of secondary amines has been studied exten-
sively, there are relatively few publications concerning the formation of
nitrosamines from primary and tertiary amines.
The nitrosation of primary amines yields monoalkylnitrosamines which
are highly unstable (Olajos and Coulston, 1978). However, small quantities
of secondary amine N-nitroso compounds are also formed in this reaction via
a mechanism which is not well understood (Fine, 1979).
Tertiary amines react with nitrous acid to yield amine type N-nitroso
compounds. Erroneous reports to the contrary have persisted for over 100
years (Fine, 1979). The reaction involves a nitrosative dealkylation; an
alkyl group must first be cleaved oxidatively to yield the secondary amine,
which then becomes nitrosated. The mechanism of this reaction has been
discussed by Lijinsky et al. (1972).
No reports were found concerning the formation of nitrosamines from
primary or tertiary amines used as boiler additives.
83
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APPENDIX C - REFERENCES
Challis, B. C., and S. A. Kyrtopoulos. 1976. Mitrosation under Allealine
Conditions. J. C. S. Chem. Comm. 178.
Challis, B. C., A. Edwards, R. Hunma, S. A. Kyrtopoulos, and J. R. Outram.
1978. Rapid Formation of N-Nitrosamines from Nitrogen Oxides under Neutral
and Alkaline Conditions. Environmental Aspects of N-Nitroso Compounds,
by E. A. Walker, M. Casteguaro, L. Griciute, and R. E. Lyle. International
Agency for Research on Cancer, Lyon, France. Scientific Publication No.
19. pp. 127-142.
x.
Edwards, G., I. Krull, M. Wolf, and D. Fine. 1978. N-Nitroso Compounds in
the Air Environment. Presented before the Division of Environmental Chemis-
try, American Chemical Society. Anaheim, California. March 12-17.
Fan, T. Y., R. Vita, and D. H. Fine. 1978. C-Nitro Compounds: A New Class
of Nitrosating Agents. Toxicology Letters 2:5-10.
Fine, D. H. 1979. N-Nitroso Compounds in the Workplace. Monitoring Toxic
Substances, by D. Schuetzle. American Chemical Society Symposium Series
No. 94. pp. 247-254.
Fine, D. H. 1978. Thermo Electron Corporation. Waltham, Massachusetts. Per-
sonal communication to A. Meiners, August 15.
Fine, D. H., and D. P. Rounbehler. 1976. N-Nitroso Compounds in the Ambient
Community Air of Baltimore, Maryland. Analytical Letters 9(6):595-604.
Keefer, L. K., and P. P. Roller. 1973. N-Nitrosation by Nitrite Ion in Neu-
tral and Basic Medium. Science 81:1245-1247.
Lijinsky, W., L. Keefer, E. Conrad, and R. Vande Bogart. 1972. Nitrosation
of Tertiary Amines and Some Biologic Implications. Journal of the National
Cancer Institute. 49:1239-1249.
Mills, A. L., and M. Alexander. 1976. Factors Affecting Dimethylnitrosamines
Formation in Samples of Soil and Water. Journal of Environmental Quality
5(4):437-440.
Mirvish, S. S. 1975. Formation of N-Nitroso Compounds: Chemistry, Kinetics,
and In Vivo Occurrence. Toxicology and Applied Pharmacology 31:325-351.
84
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Olajos, E. J., and F. Coulston. 1978. Comparative Toxicology of N-Nitroso
Compounds and their Carcinogenic Potential to Man. Ecotoxicology and En-
vironmental Safety 2:317-367.
Pitts, J. N., Jr., D. Grosjean, K. Van Cauweriberghe, J. B. Schmid, and D.
R. Fitz. 1978. Photooxidationof Aliphatic Amines under Simulated Atmos-
pheric Conditions: Formation of Nitrosamines, Nitramines, Amides, and
Photochemical Oxidant. Environmental Science and Technology 12(8):946-
953.
Singer, S. S., W. Lijinsky, and G. M. Singer. 1978. Transnitrosation: An
important Aspect of the Chemistry of Aliphatic Nitrosamines. Environmental
Aspects of N-Nitroso Compounds, by E. A. Walker, M. Castegnaro, L. Gricuite,
and R. E. Lyle. International Agency for Research on Cancer, Lyon, France.
Scientific Publication No. 19. pp. 175-182.
85
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APPENDIX D
MARKET INFORMATION ON SELECTED COMPOUNDS USED FOR CORROSION INHIBITION^
Compound (CASRN)!/ Manufacturer 1977 Production (Ib) Importer
Benzotriazole Fairmount Chemical Co. 0 to 1,000 No
syn: iH-Benzotriazole
(95-14-7) Columbia Organic 0 to 1,000 No
Chemicals
Agfa-Gevaett 0 Yes
The Sieflor Corp. "small manufacturer" Yes
Sherwin Williams "manufacturer" No
Chemicals
Mobil Oil Corp. 0 to 1,000 Yes
Unknown!/ 0 No
Cyclohexylamine Drew Chemical Corp. 10,000 to 100,000 Yes
syn: Cyclohexanamine
(108-91-8) Mobay Chemical Corp.
New Martinsville, W.Va. "manufacturer" No
Pittsburgh, Penn. not a manufacturer Yes
American Hoechst Corp. 0 Yes
Thorson Chemical Corp. 0 to 1,000 Yes
The Sieflor Corp. "small manufacturer" Yes
Sandoz Colors & Chemi- 0 Yes
cals - N. J.
Unknown!/ 0 to 1,000 Yes
(continued)
87
-------
APPENDIX D (continued)
Compound (CASRN)-'
Manufacturer
1977 Production (Ib) Importer
Cyclohexylamine (con-
tinued)
I. Schneid Inc., Ga.
Machemco Inc.
Chemical Exchange Co.,
Inc.
E. I. du Pont
Victoria, Tex.
\
Orange, Tex.
"manufacturer"
"manufacturer"
100 million to
500 million^-/
1,000 to 10,000
10,000 to 100,000
Virginia Chemicals Inc., "manufacturer"
- Portsmouth
C. Itoh and Co., Inc.
Abbott Laboratories
Dibenzylamine Uniroyal Chemical Divi-
syn: Benzenemethana- sion, Uniroyal Inc.
mine,
N-(phenylmethyl)- Miles Laboratories Inc.,
(103-49-1) Sumner Division
.Hexcel Corp., Specialty
Chemicals Division
The Ames Laboratories
Inc.
Dicyclohexylamine Kodak Park Division
syn: Cyclohexanamine,
N-cyclohexyl- BASF Wyandotte Corp.
(101-83-7)
American Hoechst
Virginia Chemicals, Inc.
Portsmouth
Koch Chemical Co.
(continued)
88
0
"manufacturer"
0 to 1,000
"manufacturer"
"manufacturer"
0 to 1,000
0 to 1,000
0
"manufacturer"
not a manufacturer
No
No
No
No
No
No
Yes
No
No
No
No
No
No
Yes
Yes
No
Yes
-------
APPENDIX D (continued)
Compound (CASRN)-/
Manufacturer
1977 Production (Ib) Importer
Dicyclohexylamine
(continued)
Abbott Laboratories
Dicyclohexylammonium Olin Corp.
Nitrite
syn: Cyclohexanamine, Northern Instruments
N-cyclohexyl-, Corp.
nitrite
(3129-91-7)
"manufacturer"
10,000 to 100,000
1,000 to 10,000
Diethylamine
s yn: E thanamine,
N-ethyl-
(109-89-8)
2-Diethylaminoethanol
syn: Ethanol,
2-(diethylami-
no)-
(100-37-8)
Ashland Chemical Co.
International Division
Pennwalt Corp.
BASF Wyandotte Corp.
0
"manufacturer"
10,000 to 100,000
Air Products & Chemicals
Inc.
Pace, Fla. "manufacturer"
St. Gabriel, La.
Uniroyal Chemical Divi-
sion, Uniroyal Inc.
Virginia Chemicals, Inc.
Portsmouth
Penwalt Corp.
Haven Chemical
Union Carbide Corp.
Alcolac Inc.
SST Corp.
The Ora Corp.
"manufacturer"
"manufacturer"
"manufacturer"
"small manufacturer"
"manufacturer"
"manufacturer"
0 to 1,000
1 million to 10 million
Proctor Chemical Co., 1 million to 10 million
Inc.
(continued)
89
No
No
No
Yes
No
Yes
No
No
Yes
No
No
No
No
No
Yes
No
No
-------
APPENDIX D (continued)
Compound (CASRN).2-/
Manufacturer
1977 Production (Ib) Importer
2-Diethylaminoethanol ICI Americas Inc.
(continued)
Unknowns.'
1,000 to 10,000 Yes
"small manufacturer" No
Diisopropylamine
syn: 2-propanamine
N-(l-methyleth-
yD-
(108-18-9)
Methylpropylamine
syn: 2-butanamine
(13952-84-6
Morpholine
(110-91-8)
Pennwalt Corp.
Union Carbide Corp.
Air Products & Chemi-
cals Inc.
ICI Americas Inc.
"manufacturer"
"manufacturer"
"manufacturer"
o /
Unknown^-'
not a manufacturer
0 to 1,000
BASF Wyandotte Corp. 0
American Hoechst Corp. 0
No
No
No
Yes
No
Yes
Yes
E. I. du Pont de
Nemours & Co.
1 million to 10 million^' No
Virginia Chemicals, Inc., "manufacturer"
Portsmouth
Henkel, Inc.
Henley & Co., Inc.
Union Carbide Corp.
BASF Wyandotte
ABC Compounding Co.,
Inc.
0 to 1,000
No
Yes
not a manufacturer Yes
0 No
100,000 to 1 million Yes
1,000 to 10,000 No
American Bio-Synthetics "small manufacturer"—' No
Corp.
Jefferson Chemical Co., Inc.
Port Neches, Tex. "manufacturer"
Conroe, Tex.
(continued)
"manufacturer"
No
No
90
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APPENDIX D (concluded)
o /
Compound (CASRN)—' Manufacturer 1977 Production (Ib) Importer
o /
Morpholine (continued) Unknown^' "small manufacturer" No
N-Nitrosodiisopropyla- Kodak Park Division 0 No
mine
syn: 1-propanamine, The Ames Laboratories 0 to 1,000 No
N-nitroso-n- Inc.
propyl-
(621-64-7)
Octadecylamine Armak Industrial Chemicals
syn: 1-octadecylamine McCook, 111. "manufacturer" No
(124-30-1)
Morris, 111. "manufacturer" NO
Ashland Chemical Company
Oakland, Calif. 0 No
Mapleton, 111. 100,000 to 1 million No
I. Schneid Inc., Ga. "manufacturer" No
Machemco Inc. "manufacturer" No
General Mills Chemicals "manufacturer" No
Inc.
Unknown!/ 1,000 to 10,000 Yes
Tolyltriazole American Hoechst Corp. not a manufacturer Yes
syn: lH-Benzotriazole,
methyl Sherwin Williams "manufacturer" No
(29385-43-1) Chemicals
I/ Based on nonconfidential information submitted to the EPA by manufacturers
and importers as of January, 1979.
2j Chemical Abstracts Service Registry Number.
_3_/ Link between information and company has been claimed to be confidential. .
4/ Chemical is manufactured and consumed on site.
91
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TECHNICAL REPORT DATA
ll'leasc read luuructions on the reverse he fore completing!
1 REPORT NO.
EPA 560/11-80-023
•1. TITLE AND SUB! I'l LIE
Volatile Corrosion Inhibitors and Boiler Water
Additives: Potential for Nitrosamine Formation
6. PERFORMING ORGANIZATION CODE
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
July 1980
7. AUTHORISi
Alfred F. Meiners, Howard Gadberry, Bonnie L. Carson
Harold P. Owens, Thomas W. Lapp
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Midwest Research Institute
425 Volker Boulevard
Kansas City, Missouri 64110
10. PROGRAM ELEMENT NO.
Task III
11. CONTRACT/GRANT NO.
68-01-3896
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Protection Agency
Office of Pesticides and Toxic Substances
Washington, D.C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
Final Rpnnrf-
Len
INTO
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
Roman Kuchkuda, Project Officer
16. ABSTRACT
Study investigated volatile corrosion inhibitors (VCIs) and the use of
amines as boiler water additives. The major VCI's are dicyclohexylammoniuni nitrite
(Dichan), "nonnitrite" Dichan substitutes, and'benzotriazole. The present market is
about 310^000 kg/year; over 90% of the use is in the preparation of impregnated paper
and other wrapping materials. Dichan can be converted to the corresponding nitrosa-
mine; commercial products can contain up to 1 ppm of the nitrosamine. Nonnitrite sub-
situtes are less likely to be converted to nitrosamines but can likely be readily
nitrosated under environmental conditions. Benzotriazole Is likely to be environmen-
tally stable and not converted to the corresponding nitrosamine. Population exposure
to VCI's is large since it is estimated that over 20 million individual items are
wrapped in VCI impregnated paper. Two cases of nitrosamine detection at levels of
100 and 90 ppm in VCI wrapping paper have been reported. A number of amines are em-
ployed for treating boiler water. The total market in 1978 was estimated to be 9,000
to 10,300 metric tons. The two most widely used neutralizing amines are cyclohexyl-
amine and morpholine; octadecylamine is the most common film-forming araine. There is
no experimental evidence to indicate whether or not nitrosamines are formed in boilers
as a result of the addition of these amines. Picogram amounts of N-nitrosomorpholine
were recently reported in the steam condensate from boilers and at several other lo-
cations at a plant which produces chemicals for the rubber industry. It was specu-
lated that a transnitrosation reaction of morpholine with N-nitrosodiphenylamine may
have resulted in the N-nitrosomorpholine.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Corrosion Inhibition
Nitrosamines
VCI
Exposure
Boiler Additives
Water Treatment
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Z. DISTRIBUTION STATEMENT
Unlimited distribution
19. SECURITY CLASS (This Report I
Unclassified
21. NO. OF PAGES
95
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
92
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