ASTM B322-99(2009)
(Guide)Standard Guide for Cleaning Metals Prior to Electroplating
Standard Guide for Cleaning Metals Prior to Electroplating
SIGNIFICANCE AND USE
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.)
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: B322 − 99 (Reapproved2009) 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 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
removal of heat-treat or mill scale are not included in these Part IV—Trouble shooting.
methods, because they are covered in practices referring to
Often, depending largely on the amount and type of soil on
specific metals. It should also be understood that while these
the workpieces as received, one or more of these stages may be
procedures are broadly applicable, particular substrates may
eliminated or modified. Usually, even with light soils, it is
require certain specific cleaning procedures.
advisable to retain multistage cleaning, thereby increasing the
life and efficiency of the cleaning solutions.
1.2 Adequate cleaning requires a proper combination of
cleaning procedures. The choice of these procedures must be
1.5 This standard does not purport to address all of the
based on a knowledge of the metals to be cleaned and of the
safety concerns, if any, associated with its use. It is the
soils to be removed. Because most experience and knowledge
responsibility of the user of this standard to establish appro-
in cleaning have been obtained by suppliers of proprietary
priate safety and health practices and determine the applica-
processes and formulations, these sources should be consulted
bility of regulatory limitations prior to use. (For more specific
before setting up a cleaning process.
safety precautionary statements see Sections 11 and 16.)
1.3 Atreatment to remove tarnish, light rust, fingerprints, or
2. Significance and Use
oxides is usually provided before immersion of the piece in the
electroplating tank. This treatment activates the metal and is
2.1 The performance and quality of electroplated articles
usually accomplished in acid baths which also serve to
depend upon the surface cleanliness and condition. Various
neutralize the residual alkaline film from alkaline cleaning.
metals are electroplated for decorative or engineering finishes.
Alkaline chelated derusting and cleaning solutions, alone or
The common electroplates applied are usually copper, nickel,
withsodiumcyanide,usedasasoakorelectrocleaner,areoften
and chromium for decorative and functional uses. Electro-
preferred before electroplating on ferrous alloys.
plated articles are used in many industries such as the marine,
automotive, plumbing fixtures, and appliance industries.
1.4 Invariably several stages are necessary to provide ad-
equate cleaning. These stages are discussed in three parts:
3. Nature of the Soil
3.1 Some of the soils commonly encountered in electroplat-
This guide is under the jurisdiction of ASTM Committee B08 on Metallic and
ing are:
Inorganic Coatingsand is the direct responsibility of Subcommittee B08.02 on Pre
Treatment.
3.1.1 Solid buffing compounds containing waxes, fatty
Current edition approved Sept. 1, 2009. Published December 2009. Originally
acids, and abrasives.
approved in 1958. Last previous edition approved in 2004 as B322 – 99(2004) .
DOI: 10.1520/B0322-99R09. 3.1.2 Liquid buffing compounds.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B322 − 99 (2009)
3.1.3 Drawing and stamping compounds including those sensitive than the“ skin” of the casting. Some surface defects
containing fillers (pigments). may not show up until cleaning and electroplating cycles are
completed.
3.1.4 Machining oils.
3.1.5 Rust-preventive slushing oils or greases.
5. Cleaner
3.1.6 Electroplater’s stop-off residues.
5.1 It is essential that proper cleaners and operational
3.1.7 Fingerprints.
conditions be selected. Attention should be given to proper
3.1.8 Dry dirt from storage or dry pickling smut formed
procurement since, even in the same category, not all cleaners
during derusting by pickling.
are equally effective. A cleaner may be very effective for one
3.1.9 Rust or oxide scales, especially admixed with oil,
group of soils, yet poor for other soils. This is true of
including heat-treat scales after oil quenching.
electrocleaners as well as soak or spray cleaners. Soil, type of
3.1.10 Phosphate coating with or without lubricant.
water, available time, rinsing facilities, type of metal, heating,
3.1.11 Smut resulting from improper vapor degreasing of
and agitation available, facilities for disposal of cleaner, and
heavily buffed work.
type of personnel and equipment all influence the selection of
3.1.12 Smut resulting from annealing parts without pre-
cleaners. Obviously, economics must be considered but an
cleaning between drawing operations.
initialorperpoundcostmustbebalancedagainstotherfactors.
3.1.13 Heat-treating salts, with or without quenching oils.
5.2 Cleaners do not work effectively indefinitely. The effec-
3.2 Consideration should be given to control of the soil. For tive life of a cleaning bath must be estimated and baths
example, efforts should be made to avoid overbuffing, leaving
discarded when exhausted. Bath life is influenced by some of
excessivecompoundonthework,oragingofthecompoundon
the factors mentioned above as well as by the volume of work
the part before cleaning. Substitution of liquid for solid buffing
processed. The concentration of the cleaner should be con-
compound, if work permits, often gives easier cleaning, if
trolled by analysis at regular intervals.
properly applied, but may require use of a different type of
6. Rinses
cleaner. Drawing compounds with polymerizing oils or white
lead pigment are to be avoided because of difficulty in
6.1 Water hardness, acidity or alkalinity, and impurities are
cleaning. Additives for lubricating and sulfurized cutting oils
important factors in rinsing (1). Distilled or demineralized
are chosen for their ability to adhebe tenaciously and are
water is preferred where impurities in rinse water must be kept
difficult to remove. Prolonged storage or drying of emulsion
to a minimum. Boiler condensate may also be used advanta-
drawing compounds after metal working should be avoided so
geously. If the plant conditions water for acidity or alkalinity
that slimy water-in-oil emulsions do not form. In-process
care must be taken to be sure the solids content is not too high
cleaning or even a hot-water flush before storage is helpful.
(Note 1). Impurities derived from processing cannot be ig-
Emulsion machining lubricants (soluble oils) should be used in
nored; that is, rinse waters must be changed frequently or
place of sulfurized cutting oils if operations permit. Lower-
overflowed continuously (Note 2). Counterflowing rinses are a
viscosity machining and rust-preventive oils are more easily
distinct advantage in obtaining good rinsing with economical
removed. Stop-off materials, when used, should be applied
use of water.
carefully in order to avoid contaminating significant surfaces.
NOTE 1—Boiler waters which contain cationic corrosion inhibitors may
The use of clean gloves should be mandatory after buffing or
be quite detrimental to the plating process.
polishing to avoid fingerprints on the work.Airborne contami-
NOTE 2—Floating oil on water can cause poor adhesion.
nants can be avoided by using covers over stored work. It is
7. Equipment
desirable to perform a cleaning operation as soon as possible
after metal forming, polishing, or buffing to reduce the de-
7.1 It is important to provide enough room in the plant for
mands on subsequent cleaning operations, because many soils
an adequate cleaning cycle. A discussion of equipment is
are more easily removed when fresh.
beyond the scope of this practice (2, 3).
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
tend to trap solid particles or buffing compositions. With die
castings, care must be exercised to avoid cutting through the
The boldface numbers in parentheses refer to the reports and papers appearing
surface by excessive buffing. The subsurface is usually more in the list of references at the end of this practice.
B322 − 99 (2009)
8.2 A dip in clean, dilute acid and reexamination are not readily accessible, the process is sometimes supplemented
desirable to avoid false water-film continuity due to adsorbed by ultrasonic cleaning in the solvent rinse chamber.
soaps. Other methods, including electroplating and testing of 10.3.2 Vapor degreasing is effective on solvent-soluble soils
the electroplate, should be used occasionally to confirm visual and chemically active lubricants. Insoluble soils (buffing grits,
metal chips and dust, etc.) are flushed away as the soluble soils
examination. (One procedure involves scrubbing with pumice
and then comparing the surface produced by this method with (greases and oils) dissolve in the solvent. It is not effective on
metallic salts, scale, carbon deposits, many inorganic soldering
that produced under production conditions.)
or welding fluxes, and fingerprints unaccompanied by oil or
PART I—PRECLEANING
grease. This process is frequently competitive in cost with wet
cleaning methods. Its lower equipment, floor space, and heat
9. Purpose
requirements offset the higher cost of solvent.
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
fingerprints and dry dust with an oily matrix to facilitate 10.4 Emulsion Cleaners—Oils and high-boiling hydrocar-
removal by alkaline cleaners.
bonssuchaskerosenehavetheabilitytodissolvemostgreases,
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
perchloroethylene; 1,1,1,-trichloroethane (methylchloroform);
solvents, unstable emulsions (diphase cleaners), invert-type
methylene chloride; or trichlorotrifluoroethane can be used for
emulsion cleaners, and stable emulsions. Additions of rust
coldcleaning.Combiningthesewithhandbrushingisexcellent
inhibitors or of alkali cleaners can be made to the water phase.
but does not lend itself to production conditions. On the other
Since agitation is important to good cleaning, the power-spray
hand, simple dipping in solvent is frequently ineffective. The
cleaners find wide applications.
chlorinated solvents are very effective for many soils, but not
10.4.2 Emulsion cleaners are used at temperatures up to
as effective in removing soap-based or other solvent-insoluble
82°C. The higher temperatures remove soils more quickly and
soils. Before electroplating, cold cleaning with solvents must
effectively, but caution must be used with cleaners containing
be followed by additional cleaning such as alkaline cleaning to
organics of low flash point. Some cleaners containing chlori-
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
methylene chloride are used for vapor degreasing. In vapor
10.5 Biological Cleaners (14)—Highly emulsifying soak
degreasing, the work is usually sprayed with clean solvent or
cleaners are combined with living microorganisms to permit
given a thorough immersion in boiling or warm solvent for
the removed oils, greases, and other complex organic com-
mechanical removal of tenacious soil or solids. This is fol-
pounds to undergo a natural process
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.