ASTM B281-88(2001)
(Practice)Standard Practice for Preparation of Copper and Copper-Base Alloys for Electroplating and Conversion Coatings
Standard Practice for Preparation of Copper and Copper-Base Alloys for Electroplating and Conversion Coatings
SCOPE
1.1 This practice is intended to serve as a guide for the proper preparation of copper and its alloys for electroplating and conversion coating. This practice is also suitable for use before autocatalytic plating. Only alloys containing at least 50 mass % copper are considered within the scope of this practice.
1.2 The wide variety of methods of mechanical finishing are not considered strictly as preparation for electroplating or conversion coating and consequently are described only briefly.
1.3 Details of electroplating and subsequent treatments for applying conversion coatings are not within the scope of this practice.
1.4 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems 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 a specific precautionary statement, see 6.5.2.
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Designation:B281–88(Reapproved 2001)
Standard Practice for
Preparation of Copper and Copper-Base Alloys for
Electroplating and Conversion Coatings
This standard is issued under the fixed designation B 281; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 4. Process Chemicals
1.1 This practice is intended to serve as a guide for the 4.1 All process chemicals are of technical grade or better.
proper preparation of copper and its alloys for electroplating Acid solutions are prepared from grade chemicals as listed in
and conversion coating. This practice is also suitable for use Appendix X1.
before autocatalytic plating. Only alloys containing at least 50 4.2 Purity of Water—High quality water is not normally
mass %copperareconsideredwithinthescopeofthispractice. required to make up and maintain the solutions utilized in this
1.2 The wide variety of methods of mechanical finishing are practice. If reused or recycled water from waste treatment
not considered strictly as preparation for electroplating or processes or from other in-plant sources is to be used, it should
conversion coating and consequently are described only be relatively free of chromium salts, oil, wetting agents, or
briefly. insoluble materials. Excessively hard water can decrease the
1.3 Details of electroplating and subsequent treatments for life and performance of many cleaning solutions and make
applying conversion coatings are not within the scope of this parts more difficult to rinse completely.
practice.
5. General Considerations
1.4 This standard does not purport to address all of the
5.1 Removal of Oxides—Oxides can be removed from as
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- fabricated, annealed, or heat-treated alloys by abrasive meth-
ods such as tumbling, burnishing, and emery set-up wheel
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. For a specific polishing and by chemical methods, such as deoxidizing
hazard statement, see 6.5.2. solutions, bright dips, and cyanide dips. The choice of method
is dependent on the resultant surface finish required, amount of
2. Referenced Documents
oxide to be removed, and the end-use properties of the article
2.1 ASTM Standards: finished.
B 322 Practice for Cleaning Metals Prior to Electroplating 5.2 Castings and Forgings—Castings and forgings requir-
ing abrasive methods to produce a desired surface finish do not
3. Significance and Use
necessarily need pickling or bright dipping. If pickled, bright
3.1 The proper preparation of copper and copper alloy dipped, or deoxidized, however, castings and other porous
surfaces for electroplating, conversion coating, or autocatalytic
parts should be thoroughly rinsed between operations to avoid
plating is often critical to the performance of the coatings. or minimize staining or stain spots. Castings or forgings
3.2 This practice outlines procedures required to produce
processed in solutions containing wetting agents, which are in
satisfactory coatings on surfaces of copper and copper alloy many proprietary products or which may be added by the
surfaces.
individual, usually require greater care in rinsing.
5.3 Stampings and Drawn Products—Stampings and drawn
work follow the same rule as castings and forgings except, for
This practice is under the jurisdiction of ASTM Committee B08 on Metallic
economy considerations, it may be advisable to pickle or
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on
Pretreatment. deoxidize before abrasive finishing if heavy oxides are present.
Current edition approved March 25, 1988. Published May 1988. Originally
published as B 281 – 53 T. Last previous edition B 281 – 82.
Annual Book of ASTM Standards, Vol 02.05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B281
5.4 Cold-Headed and Progressive Die Products—Cold- before nickel, copper, tin, chromium, and similar plating
headed products and progressive die products often require solutions, an acid dip is used. The most common dips used are
relief annealing to avoid subsequent season cracking. sulfuricacid,50mL/Lto100mL/Lbyvolume,orhydrochloric
5.5 Screw Machine Products—Screw machine products acid, 100 mL/L to 200 mL/L by volume. Fluoboric acid, 50
may be readily electroplated with only mild cleaning and acid mL/L to 100 mL/L by volume, can be used before fluoborate
dipping as they are produced from the machines. Abrasive electroplating solutions. These solutions are maintained at
methods may be applied as appropriate before cleaning and roomtemperature.Leadedcopperalloysforminsolublesaltsin
acid dipping. either sulfuric or hydrochloric acid, and therefore should be
pickled in fluoboric acid, 20 mL/L to 50 mL/L by volume, or
6. Preparation for Electroplating and Conversion nitric acid, 100 mL/L to 200 mL/L by volume.
6.5.2 Cyanide Dipping—After the work has been cleaned,
Coating
acid pickled, or acid dipped, and thoroughly rinsed, it is
6.1 Outlines of Typical Preparatory Cycles:
sometimes immersed in a 15 to 45 g/Lsodium cyanide solution
6.1.1 Vapor degrease or alkaline clean or emulsion soak
to remove slight tarnish. This step is more common if the first
clean, or tumble clean,
electroplating solution also contains cyanide. (Warning—One
6.1.2 Rinse,
should provide adequate rinsing before and after any cyanide-
6.1.3 Alkaline electroclean,
containing solution before going into an acid solution.)
6.1.4 Rinse,
6.1.5 Acid dip,
NOTE 6—Whenprocessingpartscontainingleadasanalloyconstituent,
6.1.6 Rinse, and such as free-machining brass, care should be taken not to allow lead to
accumulate in a cyanide solution beyond 50 mg/L as Pb.
6.1.7 Electroplate or conversion coat in an acid solution.
6.5.3 Deoxidizing and Bright Dipping:
NOTE 1—A bright dip, electropolish, or deoxidization may be added
6.5.3.1 Deoxidizing is usually performed to activate the
after step 6.1.4 or 6.1.2.4 followed by two agitated and running rinses
prior to step 6.1.5.
surface of the part by the removal of the oxide coating. Strong
NOTE 2—If chromium compounds are used in the bright dip or
oxidizing solutions such as mixtures of sulfuric acid and
alternatives in Note 1, additional steps will be required to ensure complete
hydrogen peroxide are used as pickling agents. Most of these
chromium removal from surfaces before any plating process.
compositions are proprietary.
NOTE 3—Additional information on procedures for cleaning of copper
6.5.3.2 Bright dipping is primarily used to improve the
or copper alloys prior to electroplating may be found in Practice B 322.
surface luster of the work. It also serves as a deoxidizing
6.2 Precleaning—Solvent or solvent-alkali emulsion-soak
solution. While proprietary processes are available one non-
cleaners can be used if the parts being electroplated can be
proprietary composition which can produce good surface luster
rinsed easily and completely; otherwise, mild alkaline cleaners
(not mirror brightness) is included inAppendix X1. The bright
and vapor degreasing should be used.
dipped parts should be rinsed thoroughly by immersion in
6.3 Electrocleaning—To produce the chemically clean sur-
several water rinses with constant agitation. A mild alkaline
face required for electroplating or subsequent coatings, an
solution may be employed to neutralize residual acids before
electrolytic cleaner may be used with the part as the anode or
immersion in any cyanide-containing solution. An excess of
cathode. Anodic cleaning, particularly of brass, may cause
hydrochloric acid in the bright dip composition must be
slight tarnishing or etching if applied for a prolonged time
avoided; otherwise, a dull finish will result.
(more than a few seconds) or at too high or too low an
operating temperature. A contaminated cathodic cleaner may
7. Striking
form a smut film on the work. The voltage at the source is
7.1 Copper Strike—In order to prevent peeling, a
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