ASTM B322-99(2020)e1

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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. (For more specific safety precautionary statements see Sections 11 and 16.)  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Oct-2020
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.02 - Pre Treatment

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: B322 − 99 (Reapproved 2020) 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.
ε NOTE—Editorial corrections were made throughout in December 2020.
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 1.4 Invariably several stages are necessary to provide ad-
equate cleaning. These stages are discussed in three parts:
1.1 This guide describes the procedure for cleaning metal
Part I—Precleaning (use of a solvent, emulsion, or alkaline
surfaces to obtain good adhesion of electrodeposited metals.
spray) to remove the bulk of the soil.
The degree of cleanliness required for metals to be electro-
Part II—Intermediate (alkaline) cleaning.
plated is greater than for most other finishes. Methods of
Part III—Final electrocleaning, to remove trace solids and
removal of heat-treat or mill scale are not included in these
especially adherent impurities.
methods, because they are covered in practices referring to
specific metals. It should also be understood that while these
Part IV—Trouble shooting.
procedures are broadly applicable, particular substrates may
Often, depending largely on the amount and type of soil on
require certain specific cleaning procedures.
the workpieces as received, one or more of these stages may be
eliminated or modified. Usually, even with light soils, it is
1.2 Adequate cleaning requires a proper combination of
advisable to retain multistage cleaning, thereby increasing the
cleaning procedures. The choice of these procedures must be
life and efficiency of the cleaning solutions.
based on a knowledge of the metals to be cleaned and of the
soils to be removed. Because most experience and knowledge
1.5 This standard does not purport to address all of the
in cleaning have been obtained by suppliers of proprietary
safety concerns, if any, associated with its use. It is the
processes and formulations, these sources should be consulted
responsibility of the user of this standard to establish appro-
before setting up a cleaning process.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.3 Atreatment to remove tarnish, light rust, fingerprints, or
(FormorespecificsafetyprecautionarystatementsseeSections
oxides is usually provided before immersion of the piece in the
11 and 16.)
electroplating tank. This treatment activates the metal and is
1.6 This international standard was developed in accor-
usually accomplished in acid baths which also serve to
dance with internationally recognized principles on standard-
neutralize the residual alkaline film from alkaline cleaning.
ization established in the Decision on Principles for the
Alkaline chelated derusting and cleaning solutions, alone or
Development of International Standards, Guides and Recom-
withsodiumcyanide,usedasasoakorelectrocleaner,areoften
mendations issued by the World Trade Organization Technical
preferred before electroplating on ferrous alloys.
Barriers to Trade (TBT) Committee.
2. Significance and Use
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
2.1 The performance and quality of electroplated articles
Treatment.
depend upon the surface cleanliness and condition. Various
Current edition approved Nov. 1, 2020. Published December 2020. Originally
metals are electroplated for decorative or engineering finishes.
approvedin1958.Lastpreviouseditionapprovedin2014asB322 – 99(2014).DOI:
10.1520/B0322-99R20E01. The common electroplates applied are usually copper, nickel,
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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B322 − 99 (2020)
and chromium for decorative and functional uses. Electro- determining factor in cleaner selection. Aluminum requires
plated articles are used in many industries such as the marine, care to avoid overetching in alkaline cleaners; both aluminum
automotive, plumbing fixtures, and appliance industries. and zinc are sensitive to pitting attack, zinc and brass to
tarnishing. Zinc die castings have surfaces that require special
3. Nature of the Soil
care because of sensitivity to attack by cleaning solutions. If
possible, design of parts should avoid small indentations that
3.1 Some of the soils commonly encountered in electroplat-
tend to trap solid particles or buffing compositions. With die
ing are:
castings, care must be exercised to avoid cutting through the
3.1.1 Solid buffing compounds containing waxes, fatty
surface by excessive buffing. The subsurface is usually more
acids, and abrasives.
sensitive than the“ skin” of the casting. Some surface defects
3.1.2 Liquid buffing compounds.
may not show up until cleaning and electroplating cycles are
3.1.3 Drawing and stamping compounds including those
completed.
containing fillers (pigments).
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.
3.1.13 Heat-treating salts, with or without quenching oils. 5.2 Cleaners do not work effectively indefinitely. The effec-
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 adhere 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
carefully in order to avoid contaminating significant surfaces. NOTE 1—Boiler waters which contain cationic corrosion inhibitors may
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
and surface finish of the metal are factors in selecting handling
The boldface numbers in parentheses refer to the reports and papers appearing
methods.Thechemicalactivityofthemetalisanimportantand in the list of references at the end of this practice.
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B322 − 99 (2020)
water-break test is most commonly used. This involves visual because it cleans by solvent action instead of chemical action;
observation after a final rinse in clear, cool water.Acontinuous there is no danger of over-cleaning or under-cleaning because
sheet of water on the part usually indicates a clean surface. of any difference in chemical activity of the metals present.
(Certain precious-metal surfaces, such as gold, may exhibit Because of the rapid penetrating action of the solvent and
water break, even though clean.) Some experience is necessary solvent vapor, this method is effective in cleaning parts
to judge the appearance of a break in the film of water. A containing recesses, blind holes, perforations, crevices, and
specific drainage time, about 30 s, should be used before welded seams. Where the soils are present on surfaces that are
observation. not readily accessible, the process is sometimes supplemented
by ultrasonic cleaning in the solvent rinse chamber.
8.2 A dip in clean, dilute acid and reexamination are
10.3.2 Vapor degreasing is effective on solvent-soluble soils
desirable to avoid false water-film continuity due to adsorbed
and chemically active lubricants. Insoluble soils (buffing grits,
soaps. Other methods, including electroplating and testing of
metal chips and dust, etc.) are flushed away as the soluble soils
the electroplate, should be used occasionally to confirm visual
(greases and oils) dissolve in the solvent. It is not effective on
examination. (One procedure involves scrubbing with pumice
metallic salts, scale, carbon deposits, many inorganic soldering
and then comparing the surface produced by this method with
or welding fluxes, and fingerprints unaccompanied by oil or
that produced under production conditions.)
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
mild electrolytic cleaning and subsequent electroplating with-
especially deposits of buffing compound or grease. It is also
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
a variety of ways including the use of straight emulsifiable
10.2 Cold Solvent (6)—Mineral spirits; trichloroethylene;
perchloroethylene; 1,1,1,-trichloroethane (methylchloroform); solvents, unstable emulsions (diphase cleaners), invert-type
emulsion cleaners, and stable emulsions. Additions of rust
methylene chloride; or trichlorotrifluoroethane can be used for
coldcleaning.Combiningthesewithhandbrushingisexcellent inhibitors or of alkali cleaners can be made to the water phase.
Since agitation is important to good cleaning, the power-spray
but does not lend itself to production conditions. On the other
hand, simple dipping in solvent is frequently ineffective. The cleaners find wide applications.
10.4.2 Emulsion cleaners are used at temperatures up to
chlorinated solvents are very effective for many soils, but not
as effective in removing soap-based or other solvent-insoluble 82 °C. The higher temperatures remove soil
...