ASTM B281-88(1995)
(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: B 281 – 88 (Reapproved 1995)
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Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
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 required to make up and maintain the solutions utilized in this
practice. If re-used or recycled water from waste treatment
1.1 This practice is intended to serve as a guide for the
processes or from other in-plant sources is to be used, it should
proper preparation of copper and its alloys for electroplating
be relatively free of chromium salts, oil, wetting agents, or
and conversion coating. This practice is also suitable for use
insoluble materials. Excessively hard water can decrease the
before autocatalytic plating. Only alloys containing at least 50
life and performance of many cleaning solutions and make
mass % copper are considered within the scope of this practice.
parts more difficult to rinse completely.
1.2 The wide variety of methods of mechanical finishing are
not considered strictly as preparation for electroplating or
5. General Considerations
conversion coating and consequently are described only
5.1 Removal of Oxides—Oxides can be removed from as
briefly.
fabricated, annealed, or heat-treated alloys by abrasive meth-
1.3 Details of electroplating and subsequent treatments for
ods such as tumbling, burnishing, and emery set-up wheel
applying conversion coatings are not within the scope of this
polishing and by chemical methods, such as deoxidizing
practice.
solutions, bright dips, and cyanide dips. The choice of method
1.4 This standard does not purport to address all of the
is dependent on the resultant surface finish required, amount of
safety concerns, if any, associated with its use. It is the
oxide to be removed, and the end-use properties of the article
responsibility of the user of this standard to establish appro-
finished.
priate safety and health practices and determine the applica-
5.2 Castings and Forgings—Castings and forgings requir-
bility of regulatory limitations prior to use. For a specific
ing abrasive methods to produce a desired surface finish do not
hazard statement, see Note 6.
necessarily need pickling or bright dipping. If pickled, bright
2. Referenced Documents dipped, or deoxidized, however, castings and other porous
parts should be thoroughly rinsed between operations to avoid
2.1 ASTM Standards:
or minimize staining or stain spots. Castings or forgings
B 322 Practice for Cleaning Metals Prior to Electroplating
processed in solutions containing wetting agents, which are in
3. Significance and Use many proprietary products or which may be added by the
individual, usually require greater care in rinsing.
3.1 The proper preparation of copper and copper alloy
5.3 Stampings and Drawn Products—Stampings and drawn
surfaces for electroplating, conversion coating, or autocatalytic
work follow the same rule as castings and forgings except, for
plating is often critical to the performance of the coatings.
economy considerations, it may be advisable to pickle or
3.2 This practice outlines procedures required to produce
deoxidize before abrasive finishing if heavy oxides are present.
satisfactory coatings on surfaces of copper and copper alloy
5.4 Cold-Headed and Progressive Die Products—Cold-
surfaces.
headed products and progressive die products often require
4. Process Chemicals
relief annealing to avoid subsequent season cracking.
5.5 Screw Machine Products—Screw machine products
4.1 All process chemicals are of technical grade or better.
may be readily electroplated with only mild cleaning and acid
Acid solutions are prepared from grade chemicals as listed in
dipping as they are produced from the machines. Abrasive
Appendix X1.
methods may be applied as appropriate before cleaning and
4.2 Purity of Water—High quality water is not normally
acid dipping.
This practice is under the jurisdiction of ASTM Committee B-8 on Metallic and
6. Preparation for Electroplating and Conversion
Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on
Coating
Substrate Preparation.
Current edition approved March 25, 1988. Published May 1988. Originally
6.1 Outlines of Typical Preparatory Cycles:
published as B 281 – 53 T. Last previous edition B 281 – 82.
6.1.1 Vapor degrease or alkaline clean or emulsion soak
Annual Book of ASTM Standards, Vol 02.05.
B 281
clean, or tumble clean, 6.5.2 Cyanide Dipping—After the work has been cleaned,
6.1.2 Rinse, acid pickled, or acid dipped, and thoroughly rinsed, it is
6.1.3 Alkaline electroclean, sometimes immersed in a 15 to 45 g/L sodium cyanide solution
6.1.4 Rinse, to remove slight tarnish. This step is more common if the first
6.1.5 Acid dip, electroplating solution also contains cyanide.
6.1.6 Rinse, and
NOTE 6—Precaution: One should provide adequate rinsing before and
6.1.7 Electroplate or conversion coat in an acid solution.
after any cyanide-containing solution before going into an acid solution.
NOTE 7—When processing parts containing lead as an alloy constituent,
NOTE 1—A bright dip, electropolish, or deoxidization may be added
such as free-machining brass, care should be taken not to allow lead to
after step 6.1.4 or 6.1.2.4 followed by two agitated and running rinses
accumulate in a cyanide solution beyond 50 mg/L as Pb.
prior to step 6.1.5.
NOTE 2—If chromium compounds are used in the bright dip or
6.5.3 Deoxidizing and Bright Dipping:
alternatives in Note 1, additional steps will be required to ensure complete
6.5.3.1 Deoxidizing is usually performed to activate the
chromium removal from surfaces before any plating process.
surface of the part by the removal of the oxide coating. Strong
NOTE 3—Additional information on procedures for cleaning of copper
oxidizing solutions such as mixtures of sulfuric acid and
or copper alloys prior to electroplating may be found in Practice B 322.
hydrogen peroxide are used as pickling agents. Most of these
6.2 Precleaning—Solvent or solvent-alkali emulsion-soak
compositions are proprietary.
cleaners can be used if the parts being electroplated can be
6.5.3.2 Bright dipping is primarily used to improve the
rinsed easily and completely; otherwise, mild alkaline cleaners
surface luster of the work. It also serves as a deoxidizing
and vapor degreasing should be used.
solution. While proprietary processes are available one non-
6.3 Electrocleaning—To produce the chemically clean sur-
proprietary composition which can produce good surface luster
face required for electroplating or subsequent coatings, an
(not mirror brightness) is included in Appendix X1. The bright
electrolytic cleaner may be used with the part as the anode or
dipped parts should be rinsed thoroughly by immersion in
cathode. Anodic cleaning, particularly of brass, may cause
several water rinses with constant agitation. A mild alkaline
slight tarnishing or etching if applied for a prolonged time
solution may be employed to neutralize residual acids before
(more than a few seconds) or at too high or too low an
immersion in any cyanide-containing solution. An excess of
operating temperature. A contaminated cathodic cleaner may
hydrochloric acid in the bright dip composition must be
form a smut film on the work. The voltage at the source is
avoided; otherwise, a dull finish will result.
usually 6 to 8 V. Separate solutions should be used for anodic
and cathodic cleaning. When a part is properly cleaned, it will
7. Striking
show a continuous liquid film upon removal from rinses after
7.1 Copper Strike—In order to prevent peeling, a copper
acid dip solutions.
strike is used before silver or nickel electroplating of leaded
copper alloys and work that has been soft soldered. A nickel
NOTE 4—Proprietary cleaners which are used in acc
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