ASTM B322-99(2014)
(Guide)Standard Guide for Cleaning Metals Prior to Electroplating
Standard Guide for Cleaning Metals Prior to Electroplating
SIGNIFICANCE AND USE
2.1 The performance and quality of electroplated articles depend upon the surface cleanliness and condition. Various metals are electroplated for decorative or engineering finishes. The common electroplates applied are usually copper, nickel, and chromium for decorative and functional uses. Electroplated articles are used in many industries such as the marine, automotive, plumbing fixtures, and appliance industries.
SCOPE
1.1 This guide describes the procedure for cleaning metal surfaces to obtain good adhesion of electrodeposited metals. The degree of cleanliness required for metals to be electroplated is greater than for most other finishes. Methods of removal of heat-treat or mill scale are not included in these methods, because they are covered in practices referring to specific metals. It should also be understood that while these procedures are broadly applicable, particular substrates may require certain specific cleaning procedures.
1.2 Adequate cleaning requires a proper combination of cleaning procedures. The choice of these procedures must be based on a knowledge of the metals to be cleaned and of the soils to be removed. Because most experience and knowledge in cleaning have been obtained by suppliers of proprietary processes and formulations, these sources should be consulted before setting up a cleaning process.
1.3 A treatment to remove tarnish, light rust, fingerprints, or oxides is usually provided before immersion of the piece in the electroplating tank. This treatment activates the metal and is usually accomplished in acid baths which also serve to neutralize the residual alkaline film from alkaline cleaning. Alkaline chelated derusting and cleaning solutions, alone or with sodium cyanide, used as a soak or electrocleaner, are often preferred before electroplating on ferrous alloys.
1.4 Invariably several stages are necessary to provide adequate cleaning. These stages are discussed in three parts:
Part I—Precleaning (use of a solvent, emulsion, or alkaline spray) to remove the bulk of the soil.
Part II—Intermediate (alkaline) cleaning.
Part III—Final electrocleaning, to remove trace solids and especially adherent impurities.
Part IV—Trouble shooting.
Often, depending largely on the amount and type of soil on the workpieces as received, one or more of these stages may be eliminated or modified. Usually, even with light soils, it is advisable to retain multistage cleaning, thereby increasing the life and efficiency of the cleaning solutions.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (For more specific safety precautionary statements see Sections 11 and 16.)
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Designation: B322 − 99 (Reapproved 2014) Endorsed by American
Electroplaters’ Society
Endorsed by National
Association of Metal Finishers
Standard Guide for
Cleaning Metals Prior to Electroplating
This standard is issued under the fixed designation B322; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
INTRODUCTION
This guide is intended to illustrate general principles of cleaning prior to electroplating. It is not
meant to apply to every specific application. In specific cases, cleaning practice may depart from the
general principles given in this guide.
1. Scope Part I—Precleaning (use of a solvent, emulsion, or alkaline
spray) to remove the bulk of the soil.
1.1 This guide describes the procedure for cleaning metal
Part II—Intermediate (alkaline) cleaning.
surfaces to obtain good adhesion of electrodeposited metals.
Part III—Final electrocleaning, to remove trace solids and
The degree of cleanliness required for metals to be electro-
especially adherent impurities.
plated is greater than for most other finishes. Methods of
Part IV—Trouble shooting.
removal of heat-treat or mill scale are not included in these
Often, depending largely on the amount and type of soil on
methods, because they are covered in practices referring to
the workpieces as received, one or more of these stages may be
specific metals. It should also be understood that while these
eliminated or modified. Usually, even with light soils, it is
procedures are broadly applicable, particular substrates may
advisable to retain multistage cleaning, thereby increasing the
require certain specific cleaning procedures.
life and efficiency of the cleaning solutions.
1.2 Adequate cleaning requires a proper combination of
1.5 This standard does not purport to address all of the
cleaning procedures. The choice of these procedures must be
safety concerns, if any, associated with its use. It is the
based on a knowledge of the metals to be cleaned and of the
responsibility of the user of this standard to establish appro-
soils to be removed. Because most experience and knowledge
priate safety and health practices and determine the applica-
in cleaning have been obtained by suppliers of proprietary
bility of regulatory limitations prior to use. (For more specific
processes and formulations, these sources should be consulted
safety precautionary statements see Sections 11 and 16.)
before setting up a cleaning process.
2. Significance and Use
1.3 Atreatment to remove tarnish, light rust, fingerprints, or
oxides is usually provided before immersion of the piece in the
2.1 The performance and quality of electroplated articles
electroplating tank. This treatment activates the metal and is
depend upon the surface cleanliness and condition. Various
usually accomplished in acid baths which also serve to
metals are electroplated for decorative or engineering finishes.
neutralize the residual alkaline film from alkaline cleaning.
The common electroplates applied are usually copper, nickel,
Alkaline chelated derusting and cleaning solutions, alone or
and chromium for decorative and functional uses. Electro-
withsodiumcyanide,usedasasoakorelectrocleaner,areoften
plated articles are used in many industries such as the marine,
preferred before electroplating on ferrous alloys.
automotive, plumbing fixtures, and appliance industries.
1.4 Invariably several stages are necessary to provide ad-
3. Nature of the Soil
equate cleaning. These stages are discussed in three parts:
3.1 Some of the soils commonly encountered in electroplat-
ing are:
3.1.1 Solid buffing compounds containing waxes, fatty
This guide is under the jurisdiction of ASTM Committee B08 on Metallic and
Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on Pre
acids, and abrasives.
Treatment.
3.1.2 Liquid buffing compounds.
Current edition approved Nov. 1, 2014. Published November 2014. Originally
3.1.3 Drawing and stamping compounds including those
approvedin1958.Lastpreviouseditionapprovedin2009asB322 – 99(2009).DOI:
10.1520/B0322-99R14. containing fillers (pigments).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B322 − 99 (2014)
3.1.4 Machining oils. 5. Cleaner
3.1.5 Rust-preventive slushing oils or greases.
5.1 It is essential that proper cleaners and operational
3.1.6 Electroplater’s stop-off residues.
conditions be selected. Attention should be given to proper
3.1.7 Fingerprints.
procurement since, even in the same category, not all cleaners
3.1.8 Dry dirt from storage or dry pickling smut formed
are equally effective. A cleaner may be very effective for one
during derusting by pickling.
group of soils, yet poor for other soils. This is true of
3.1.9 Rust or oxide scales, especially admixed with oil,
electrocleaners as well as soak or spray cleaners. Soil, type of
including heat-treat scales after oil quenching.
water, available time, rinsing facilities, type of metal, heating,
3.1.10 Phosphate coating with or without lubricant.
and agitation available, facilities for disposal of cleaner, and
3.1.11 Smut resulting from improper vapor degreasing of
type of personnel and equipment all influence the selection of
heavily buffed work.
cleaners. Obviously, economics must be considered but an
3.1.12 Smut resulting from annealing parts without pre-
initialorperpoundcostmustbebalancedagainstotherfactors.
cleaning between drawing operations.
5.2 Cleaners do not work effectively indefinitely. The effec-
3.1.13 Heat-treating salts, with or without quenching oils.
tive life of a cleaning bath must be estimated and baths
3.2 Consideration should be given to control of the soil. For
discarded when exhausted. Bath life is influenced by some of
example, efforts should be made to avoid overbuffing, leaving
the factors mentioned above as well as by the volume of work
excessivecompoundonthework,oragingofthecompoundon
processed. The concentration of the cleaner should be con-
the part before cleaning. Substitution of liquid for solid buffing
trolled by analysis at regular intervals.
compound, if work permits, often gives easier cleaning, if
properly applied, but may require use of a different type of
6. Rinses
cleaner. Drawing compounds with polymerizing oils or white
6.1 Water hardness, acidity or alkalinity, and impurities are
lead pigment are to be avoided because of difficulty in
important factors in rinsing (1). Distilled or demineralized
cleaning. Additives for lubricating and sulfurized cutting oils
water is preferred where impurities in rinse water must be kept
are chosen for their ability to adhebe tenaciously and are
to a minimum. Boiler condensate may also be used advanta-
difficult to remove. Prolonged storage or drying of emulsion
geously. If the plant conditions water for acidity or alkalinity
drawing compounds after metal working should be avoided so
care must be taken to be sure the solids content is not too high
that slimy water-in-oil emulsions do not form. In-process
(Note 1). Impurities derived from processing cannot be ig-
cleaning or even a hot-water flush before storage is helpful.
nored; that is, rinse waters must be changed frequently or
Emulsion machining lubricants (soluble oils) should be used in
overflowed continuously (Note 2). Counterflowing rinses are a
place of sulfurized cutting oils if operations permit. Lower-
distinct advantage in obtaining good rinsing with economical
viscosity machining and rust-preventive oils are more easily
use of water.
removed. Stop-off materials, when used, should be applied
NOTE 1—Boiler waters which contain cationic corrosion inhibitors may
carefully in order to avoid contaminating significant surfaces.
be quite detrimental to the plating process.
The use of clean gloves should be mandatory after buffing or
NOTE 2—Floating oil on water can cause poor adhesion.
polishing to avoid fingerprints on the work.Airborne contami-
nants can be avoided by using covers over stored work. It is
7. Equipment
desirable to perform a cleaning operation as soon as possible
7.1 It is important to provide enough room in the plant for
after metal forming, polishing, or buffing to reduce the de-
an adequate cleaning cycle. A discussion of equipment is
mands on subsequent cleaning operations, because many soils
beyond the scope of this practice (2, 3).
are more easily removed when fresh.
8. Criteria of Cleanliness
4. Metal
8.1 This subject has been treated exhaustively in the litera-
4.1 The properties of the metal and the method of fabrica-
ture (4). The atomizer test is the most sensitive one, but the
tion and handling of parts play a role in cleaning. The softness
water-break test is most commonly used. This involves visual
and surface finish of the metal are factors in selecting handling
observation after a final rinse in clear, cool water.Acontinuous
methods.Thechemicalactivityofthemetalisanimportantand
sheet of water on the part usually indicates a clean surface.
determining factor in cleaner selection. Aluminum requires
(Certain precious-metal surfaces, such as gold, may exhibit
care to avoid overetching in alkaline cleaners; both aluminum
water break, even though clean.) Some experience is necessary
and zinc are sensitive to pitting attack, zinc and brass to
to judge the appearance of a break in the film of water. A
tarnishing. Zinc die castings have surfaces that require special
specific drainage time, about 30 s, should be used before
care because of sensitivity to attack by cleaning solutions. If
observation.
possible, design of parts should avoid small indentations that
8.2 A dip in clean, dilute acid and reexamination are
tend to trap solid particles or buffing compositions. With die
desirable to avoid false water-film continuity due to adsorbed
castings, care must be exercised to avoid cutting through the
soaps. Other methods, including electroplating and testing of
surface by excessive buffing. The subsurface is usually more
sensitive than the“ skin” of the casting. Some surface defects
may not show up until cleaning and electroplating cycles are
The boldface numbers in parentheses refer to the reports and papers appearing
completed. in the list of references at the end of this practice.
B322 − 99 (2014)
the electroplate, should be used occasionally to confirm visual metal chips and dust, etc.) are flushed away as the soluble soils
examination. (One procedure involves scrubbing with pumice (greases and oils) dissolve in the solvent. It is not effective on
and then comparing the surface produced by this method with metallic salts, scale, carbon deposits, many inorganic soldering
that produced under production conditions.) or welding fluxes, and fingerprints unaccompanied by oil or
grease. This process is frequently competitive in cost with wet
PART I—PRECLEANING
cleaning methods. Its lower equipment, floor space, and heat
requirements offset the higher cost of solvent.
9. Purpose
10.3.3 For some applications (steel stampings, buffed zinc-
9.1 Precleaning is designed to remove a large excess of soil,
base die castings, etc.), the degreased work can go directly to
especially deposits of buffing compound or grease. It is also
mild electrolytic cleaning and subsequent electroplating with-
useful in reducing the viscosity of waxes and heavy oils, to
out the need for an intermediate alkaline cleaning step.
enablelatercleaning stages to be more effective, or tosurround
10.4 Emulsion Cleaners—Oils and high-boiling hydrocar-
fingerprints and dry dust with an oily matrix to facilitate
bonssuchaskerosenehavetheabilitytodissolvemostgreases,
removal by alkaline cleaners.
particularly at high temperatures. The addition of emulsifiers,
soaps, and wetting agents enhances the penetrating power of
10. Types
the organic solvent and permits removal of the latter and
10.1 Cold solvent, vapor degreasing, emulsifiable solvent,
associated soil by power flushing. Further, intimate contact of
solvent emulsion spray, invert-type emulsion cleaners, or hot
the metal surface with the aqueous phase permits removal of
alkaline spray with or without solvent emulsion can be used
materials not soluble in the hydrocarbon phase.
(5).
10.4.1 The principle of emulsion cleaning can be applied in
10.2 Cold Solvent (6)—Mineral spirits; trichloroethylene; a variety of ways including the use of straight emulsifiable
solvents, unstable emulsions (diphase cleaners), invert-type
perchloroethylene; 1,1,1,-trichloroethane (methylchloroform);
methylene chloride; or trichlorotrifluoroethane can be used for emulsion cleaners, and stable emulsions. Additions of rust
inhibitors or of alkali cleaners can be made to the water phase.
coldcleaning.Combiningthesewithhandbrushingisexcellent
but does not lend itself to production conditions. On the other Since agitation is important to good cleaning, the power-spray
cleaners find wide applications.
hand, simple dipping in solvent is frequently ineffective. The
chlorinated solvents are very effective for many soils, but not 10.4.2 Emulsion cleaners are used at temperatures up to
82°C. The higher temperatures remove soils more quickly and
as effective in removing soap-based or other solvent-insoluble
soils. Before electroplating, cold cleaning with solvents must effectively, but caution must be used with cleaners containing
organics of low flash point. Some cleaners containing chlori-
be followed by additional cleaning such as alkaline cleaning to
remove slight oily residues. nated solvents are used above the flash point of some of the
components since the chlorinated portion will volatilize to
10.3 Vapor Degreasing (7)—Trichloroethylene and, to a
extinguish flashes.
lesser extent, perchloroethylene, trichlorotrifluoroethane, and
10.5 Biological Cleaners (8)—Highly emulsifying soak
methylene chloride are used for vapor degreasing. In vapor
degreasing, the work is usually sprayed with clean solvent or cleaners are combined with living microorganisms to permit
the removed oils, greases, and other complex organic com-
given a thorough immersion in boiling or warm solvent for
mechanical removal of tenacious soil or solids. This is fol- pounds to undergo a natural process known as bioremediation.
Living microbes break down organic compounds, such as oil
lowed by immersion in cold solvent to cool the parts. Then
and grease into carbon dioxide and water and the cleaners, if
follows exposure to condensation of hot, clean
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: B322 − 99 (Reapproved 2009) B322 − 99 (Reapproved 2014) Endorsed by American
Electroplaters’ Society
Endorsed by National
Association of Metal Finishers
Standard Guide for
Cleaning Metals Prior to Electroplating
This standard is issued under the fixed designation B322; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
INTRODUCTION
This guide is intended to illustrate general principles of cleaning prior to electroplating. It is not
meant to apply to every specific application. In specific cases, cleaning practice may depart from the
general principles given in this guide.
1. Scope
1.1 This guide describes the procedure for cleaning metal surfaces to obtain good adhesion of electrodeposited metals. The
degree of cleanliness required for metals to be electroplated is greater than for most other finishes. Methods of removal of heat-treat
or mill scale are not included in these methods, because they are covered in practices referring to specific metals. It should also
be understood that while these procedures are broadly applicable, particular substrates may require certain specific cleaning
procedures.
1.2 Adequate cleaning requires a proper combination of cleaning procedures. The choice of these procedures must be based on
a knowledge of the metals to be cleaned and of the soils to be removed. Because most experience and knowledge in cleaning have
been obtained by suppliers of proprietary processes and formulations, these sources should be consulted before setting up a
cleaning process.
1.3 A treatment to remove tarnish, light rust, fingerprints, or oxides is usually provided before immersion of the piece in the
electroplating tank. This treatment activates the metal and is usually accomplished in acid baths which also serve to neutralize the
residual alkaline film from alkaline cleaning. Alkaline chelated derusting and cleaning solutions, alone or with sodium cyanide,
used as a soak or electrocleaner, are often preferred before electroplating on ferrous alloys.
1.4 Invariably several stages are necessary to provide adequate cleaning. These stages are discussed in three parts:
Part I—Precleaning (use of a solvent, emulsion, or alkaline spray) to remove the bulk of the soil.
Part II—Intermediate (alkaline) cleaning.
Part III—Final electrocleaning, to remove trace solids and especially adherent impurities.
Part IV—Trouble shooting.
Often, depending largely on the amount and type of soil on the workpieces as received, one or more of these stages may be
eliminated or modified. Usually, even with light soils, it is advisable to retain multistage cleaning, thereby increasing the life and
efficiency of the cleaning solutions.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use. (For more specific safety precautionary statements see Sections 11 and 16.)
2. Significance and Use
2.1 The performance and quality of electroplated articles depend upon the surface cleanliness and condition. Various metals are
electroplated for decorative or engineering finishes. The common electroplates applied are usually copper, nickel, and chromium
for decorative and functional uses. Electroplated articles are used in many industries such as the marine, automotive, plumbing
fixtures, and appliance industries.
This guide is under the jurisdiction of ASTM Committee B08 on Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on Pre
Treatment.
Current edition approved Sept. 1, 2009Nov. 1, 2014. Published December 2009November 2014. Originally approved in 1958. Last previous edition approved in 20042009
as B322 – 99(2004) . (2009). DOI: 10.1520/B0322-99R09.10.1520/B0322-99R14.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B322 − 99 (2014)
3. Nature of the Soil
3.1 Some of the soils commonly encountered in electroplating are:
3.1.1 Solid buffing compounds containing waxes, fatty acids, and abrasives.
3.1.2 Liquid buffing compounds.
3.1.3 Drawing and stamping compounds including those containing fillers (pigments).
3.1.4 Machining oils.
3.1.5 Rust-preventive slushing oils or greases.
3.1.6 Electroplater’s stop-off residues.
3.1.7 Fingerprints.
3.1.8 Dry dirt from storage or dry pickling smut formed during derusting by pickling.
3.1.9 Rust or oxide scales, especially admixed with oil, including heat-treat scales after oil quenching.
3.1.10 Phosphate coating with or without lubricant.
3.1.11 Smut resulting from improper vapor degreasing of heavily buffed work.
3.1.12 Smut resulting from annealing parts without precleaning between drawing operations.
3.1.13 Heat-treating salts, with or without quenching oils.
3.2 Consideration should be given to control of the soil. For example, efforts should be made to avoid overbuffing, leaving
excessive compound on the work, or aging of the compound on the part before cleaning. Substitution of liquid for solid buffing
compound, if work permits, often gives easier cleaning, if properly applied, but may require use of a different type of cleaner.
Drawing compounds with polymerizing oils or white lead pigment are to be avoided because of difficulty in cleaning. Additives
for lubricating and sulfurized cutting oils are chosen for their ability to adhebe tenaciously and are difficult to remove. Prolonged
storage or drying of emulsion drawing compounds after metal working should be avoided so that slimy water-in-oil emulsions do
not form. In-process cleaning or even a hot-water flush before storage is helpful. Emulsion machining lubricants (soluble oils)
should be used in place of sulfurized cutting oils if operations permit. Lower-viscosity machining and rust-preventive oils are more
easily removed. Stop-off materials, when used, should be applied carefully in order to avoid contaminating significant surfaces.
The use of clean gloves should be mandatory after buffing or polishing to avoid fingerprints on the work. Airborne contaminants
can be avoided by using covers over stored work. It is desirable to perform a cleaning operation as soon as possible after metal
forming, polishing, or buffing to reduce the demands on subsequent cleaning operations, because many soils are more easily
removed when fresh.
4. Metal
4.1 The properties of the metal and the method of fabrication and handling of parts play a role in cleaning. The softness and
surface finish of the metal are factors in selecting handling methods. The chemical activity of the metal is an important and
determining factor in cleaner selection. Aluminum requires care to avoid overetching in alkaline cleaners; both aluminum and zinc
are sensitive to pitting attack, zinc and brass to tarnishing. Zinc die castings have surfaces that require special care because of
sensitivity to attack by cleaning solutions. If possible, design of parts should avoid small indentations that tend to trap solid
particles or buffing compositions. With die castings, care must be exercised to avoid cutting through the surface by excessive
buffing. The subsurface is usually more sensitive than the“ skin” of the casting. Some surface defects may not show up until
cleaning and electroplating cycles are completed.
5. Cleaner
5.1 It is essential that proper cleaners and operational conditions be selected. Attention should be given to proper procurement
since, even in the same category, not all cleaners are equally effective. A cleaner may be very effective for one group of soils, yet
poor for other soils. This is true of electrocleaners as well as soak or spray cleaners. Soil, type of water, available time, rinsing
facilities, type of metal, heating, and agitation available, facilities for disposal of cleaner, and type of personnel and equipment all
influence the selection of cleaners. Obviously, economics must be considered but an initial or per pound cost must be balanced
against other factors.
5.2 Cleaners do not work effectively indefinitely. The effective life of a cleaning bath must be estimated and baths discarded
when exhausted. Bath life is influenced by some of the factors mentioned above as well as by the volume of work processed. The
concentration of the cleaner should be controlled by analysis at regular intervals.
6. Rinses
6.1 Water hardness, acidity or alkalinity, and impurities are important factors in rinsing (1). Distilled or demineralized water
is preferred where impurities in rinse water must be kept to a minimum. Boiler condensate may also be used advantageously. If
the plant conditions water for acidity or alkalinity care must be taken to be sure the solids content is not too high (Note 1).
The boldface numbers in parentheses refer to the reports and papers appearing in the list of references at the end of this practice.
B322 − 99 (2014)
Impurities derived from processing cannot be ignored; that is, rinse waters must be changed frequently or overflowed continuously
(Note 2). Counterflowing rinses are a distinct advantage in obtaining good rinsing with economical use of water.
NOTE 1—Boiler waters which contain cationic corrosion inhibitors may be quite detrimental to the plating process.
NOTE 2—Floating oil on water can cause poor adhesion.
7. Equipment
7.1 It is important to provide enough room in the plant for an adequate cleaning cycle. A discussion of equipment is beyond
the scope of this practice (2, 3).
8. Criteria of Cleanliness
8.1 This subject has been treated exhaustively in the literature (4). The atomizer test is the most sensitive one, but the
water-break test is most commonly used. This involves visual observation after a final rinse in clear, cool water. A continuous sheet
of water on the part usually indicates a clean surface. (Certain precious-metal surfaces, such as gold, may exhibit water break, even
though clean.) Some experience is necessary to judge the appearance of a break in the film of water. A specific drainage time, about
30 s, should be used before observation.
8.2 A dip in clean, dilute acid and reexamination are desirable to avoid false water-film continuity due to adsorbed soaps. Other
methods, including electroplating and testing of the electroplate, should be used occasionally to confirm visual examination. (One
procedure involves scrubbing with pumice and then comparing the surface produced by this method with that produced under
production conditions.)
PART I—PRECLEANING
9. Purpose
9.1 Precleaning is designed to remove a large excess of soil, especially deposits of buffing compound or grease. It is also useful
in reducing the viscosity of waxes and heavy oils, to enable later cleaning stages to be more effective, or to surround fingerprints
and dry dust with an oily matrix to facilitate removal by alkaline cleaners.
10. Types
10.1 Cold solvent, vapor degreasing, emulsifiable solvent, solvent emulsion spray, invert-type emulsion cleaners, or hot alkaline
spray with or without solvent emulsion can be used (5).
10.2 Cold Solvent (6)—Mineral spirits; trichloroethylene; perchloroethylene; 1,1,1,-trichloroethane (methylchloroform); meth-
ylene chloride; or trichlorotrifluoroethane can be used for cold cleaning. Combining these with hand brushing is excellent but does
not lend itself to production conditions. On the other hand, simple dipping in solvent is frequently ineffective. The chlorinated
solvents are very effective for many soils, but not as effective in removing soap-based or other solvent-insoluble soils. Before
electroplating, cold cleaning with solvents must be followed by additional cleaning such as alkaline cleaning to remove slight oily
residues.
10.3 Vapor Degreasing (7)—Trichloroethylene and, to a lesser extent, perchloroethylene, trichlorotrifluoroethane, and
methylene chloride are used for vapor degreasing. In vapor degreasing, the work is usually sprayed with clean solvent or given
a thorough immersion in boiling or warm solvent for mechanical removal of tenacious soil or solids. This is followed by immersion
in cold solvent to cool the parts. Then follows exposure to condensation of hot, clean solvent vapors on the work. This final step
also removes any last traces of oil and grease and dries the part. For removal of caked-on oils and compounds, a predip in cool
solvent can be used to wet and loosen the soil before the degreasing operation.
10.3.1 Vapor degreasing can be used to clean all types of metal, including steel, steel alloys, light metal alloys, special bronze,
nonferrous metals, nickel, and titanium. This method simplifies the cleaning of parts containing several metals because it cleans
by solvent action instead of chemical action; there is no danger of over-cleaning or under-cleaning because of any difference in
chemical activity of the metals present. Because of the rapid penetrating action of the solvent and solvent vapor, this method is
effective in cleaning parts containing recesses, blind holes, perforations, crevices, and welded seams. Where the soils are present
on surfaces that are not readily accessible, the process is sometimes supplemented by ultrasonic cleaning in the solvent rinse
chamber.
10.3.2 Vapor degreasing is effective on solvent-soluble soils and chemically active lubricants. Insoluble soils (buffing grits,
metal chips and dust, etc.) are flushed away as the soluble soils (greases and oils) dissolve in the solvent. It is not effective on
metallic salts, scale, carbon deposits, many inorganic soldering or welding fluxes, and fingerprints unaccompanied by oil or grease.
This process is frequently competitive in cost with wet cleaning methods. Its lower equipment, floor space, and heat requirements
offset the higher cost of solvent.
10.3.3 For some applications (steel stampings, buffed zinc-base die castings, etc.), the degreased work can go directly to mild
electrolytic cleaning and subsequent electroplating without the need for an intermediate alkaline cleaning step.
10.4 Emulsion Cleaners—Oil
...
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