ASTM B254-92(1998)
(Practice)Standard Practice for Preparation of and Electroplating on Stainless Steel
Standard Practice for Preparation of and Electroplating on Stainless Steel
SCOPE
1.1 Various metals are electrodeposited on stainless steel for color matching, lubrication during cold heading, spring-coiling and wire-drawing operations, reduction of scaling at high temperatures, improvement of wettability (as in fountain pens), improvement of heat and electrical conductance, prevention of galling, jewelry decoration, and prevention of superficial rusting.
1.2 This practice is presented as an aid to electroplaters and finishing engineers, confronted with problems inherent in the electrodeposition of metals on stainless steel. It is not a standardized procedure but a guide to the production of smooth adherent electrodeposits on stainless steel.
1.3 This standard does not purport to address all of the safety problems, 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.
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Endorsed by American
Designation: B 254 – 92 (Reapproved 1998) Electroplaters’ Society
Endorsed by National Associa-
tion of Metal Finishers
Standard Practice for
Preparation of and Electroplating on Stainless Steel
This standard is issued under the fixed designation B 254; 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 penetrated, it protects stainless steel against corrosion. An
adherent electrodeposit cannot be obtained over the oxide film
1.1 Various metals are electrodeposited on stainless steel for
normally present on stainless steel. However, once this film is
color matching, lubrication during cold heading, spring-coiling
removed by surface activation and kept from reforming while
and wire-drawing operations, reduction of scaling at high
the surface is covered with an electrodeposit, any of the
temperatures, improvement of wettability (as in fountain pens),
commonly electroplated metals may be electrodeposited suc-
improvement of heat and electrical conductance, prevention of
cessfully on stainless steel.
galling, jewelry decoration, and prevention of superficial
3.3 Where the finished product is to be subjected to severe
rusting.
exposure, the deposit produced by the proposed electroplating
1.2 This practice is presented as an aid to electroplaters and
sequence should be tested under similar exposure conditions
finishing engineers, confronted with problems inherent in the
before adoption, to determine whether the natural corrosion
electrodeposition of metals on stainless steel. It is not a
resistance of the stainless steel has been impaired by the
standardized procedure but a guide to the production of smooth
presence of the electrodeposit.
adherent electrodeposits on stainless steel.
1.3 This standard does not purport to address all of the
4. Nature of Cleaning
safety problems, if any, associated with its use. It is the
4.1 The preparation of stainless steel for electroplating
responsibility of the user of this standard to establish appro-
involves three basic steps in the following order:
priate safety and health practices and determine the applica-
4.1.1 Removal of scale. If scale removal is necessary, one of
bility of regulatory limitations prior to use.
the methods outlined in Appendix X2 may be used (Note 1).
2. Referenced Documents See also Practice A 380.
4.1.2 Removal of oil, grease, or other foreign material by
2.1 ASTM Standards:
cleaning, and
A 380 Practice for Cleaning, Descaling, and Passivation of
4.1.3 Activation immediately before electroplating.
Stainless Steel Parts, Equipment, and Systems
4.2 Precleaning—Removal of fabricating lubricants and
3. Nature of Stainless Steel
finishing compounds from the stainless steel may have to be
undertaken immediately following the fabrication or finishing
3.1 Because previous metal treatment may have a more
operation (Note 2).
pronounced effect on the final finish when stainless steel is
4.3 Electrocleaning—Anodic cleaning is generally pre-
being electroplated, the metal finisher should become ac-
ferred (Note 3).
quainted with the fabrication procedure, grade, and mill finish
4.4 Metal Lubricants—Metal lubricants such as copper,
of the stainless steel with which he is working before outlining
lead, or cadmium, applied to stainless steel wire for cold
his electrodeposition procedure (see Appendix X1).
heading, wire drawing, or spring forming are removed by
3.2 Stainless steel surfaces are normally resistant to a wide
immersion in a solution of 200 mL of concentrated, 67 mass %,
variety of corrosive elements. This property is the result of a
nitric acid (density 1.40 g/mL) diluted to 1 L at 50 to 60°C. See
thin transparent film of oxides present on the surface. Because
Practice A 380.
this film rapidly reforms after it has been stripped off or
NOTE 1—Oil, grease or other fabricating lubricants should be removed
by cleaning before heat treating.
This practice is under the jurisdiction of ASTM Committee B-8 on Metallic and
NOTE 2—Spray cleaning with a nozzle pressure of 200 to 400 kPa (30
Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on
to 60 psi) in a power washer, using an alkaline or emulsion-type cleaner,
Substrate Preparation.
is the generally preferred method, especially for the removal of heavy
Current edition approved Jan. 15, 1992. Published May 1992. Originally
drawing, buffing, or polishing compounds. Soak cleaning or vapor
published as B 254–51 T. Last previous edition B 254–79 (1985).
degreasing may also be used. Extreme examples of such compounds are
Annual Book of ASTM Standards, Vol 01.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B 254
drawing or stamping lubricants containing unsaturated oils, which if left
7.4.1 Sulfuric acid 50 to 500 mL/L
on the surface, form by air-oxidation tenacious films that are very difficult
Water to 1 L
Temperature room
to remove.
Time 1 to 5 min
NOTE 3—When brightness is important, alkalinity, current density, and
Current density 0.54 A/dm
temperature should be kept as low as the part will permit. This is an
Anodes pure lead
A
essential requirement when cleaning work on racks bearing auxiliary lead
7.4.2 Hydrochloric acid 50 to 500 mL/L
anodes or when high chromium alloys (such as UNS Types S44200 and Water to 1 L
Temperature room
S44600) are being cleaned.
Time 1 to 5 min
Current density 2.15 A/dm
5. Cleaning Solutions
Anodes electrolytic nickel strip or nickel
bar
5.1 The types of solution control, electrodes, heating coils,
A
See Patent No. 2,133,996.
and rinse tanks normally used for cleaning carbon steel are
7.4.3 After immersion in a solution containing 100 to 300 mL/L of hydrochlo-
satisfactory for stainless steel. Equipment previously used for
ric acid diluted to 1 L at room temperature for 30 to 60 s, treat cathodically in:
Sulfuric acid 50 to 500 mL/L
the cleaning or processing of carbon steel should not be used.
Water to 1 L
See Practice A 380.
Temperature room
Current 0.54 to 2.7 A/dm
Anodes pure lead
6. Racking
7.5 Immersion Treatments:
6.1 The general principles of good racking as used in
7.5.1 Immerse in a solution of sulfuric acid containing 200
chromium electroplating processes apply. However, the high
to 500 mL of acid diluted to 1 L at 65 to 80°C (with the higher
electrical resistance of stainless steel requires rack construction
temperature for the lower concentration) for at least 1 min after
methods that minimize potential contact problems and increase
gassing starts. If gassing does not start within 1 min after the
the number of contact points.
parts have been immersed, touch them with a carbon-steel bar
NOTE 4—Because of the high electrical resistance of stainless steel,
or rod. This activation treatment will produce a dark, adherent
especially in fine-coiled wire articles such as watch bands, chains, jewelry,
smut that is removed in the electroplating bath. A cathodic
etc., it is necessary to provide a larger number of contacts. As an example,
current of at least 0.54 A/dm may be used to accelerate
a watch band 110 mm long made of 1.0-mm diameter wire has been found
activation. Lead anodes are suitable for this solution.
to require at least three contacts.
7.5.2 Immerse in the following solution:
7. Activation
Hydrochloric acid 1 mL
Sulfuric acid 10 mL
7.1 After the cleaning operation and before the electroplat-
Water to 1 L
ing operation, the parts must be completely activated, that is,
Temperature room
the thin transparent film of oxides must be removed from the Time 26 s
surface to be electroplated (Note 5). This film will reform if the
NOTE 7—This practice has been used with success for chromium
parts are allowed to dry or are exposed to oxygen-containing
electroplating on stainless steel automobile parts in a conveyorized
solutions. For this reason, the shortest interval practicable process. It is not recommended before copper or nickel electroplating.
should elapse between the time the parts are removed from the
7.6 Simultaneous Activation-Electroplating Treatments:
activating solution and covered by the electrodeposit, unless a
A
7.6.1 Nickel chloride 240 g
simultaneous activation-electroplating procedure is used.
Hydrochloric acid 85 mL
Iron should not exceed
NOTE 5—The etching practice may be more severe for nondecorative
7.5 g/ L
applications than for decorative applications.
Water to 1 L
Temperature room
7.2 The following activating procedures have been used.
Electrodes nickel
A
The procedure selected will depend upon the nature of the part See U. S. Patent No. 2,285,548-9.
7.6.1.1 Anodic Treatment:
and preceding or subsequent processes (see 7.7). In the
following solution formulas, the concentrations are expressed
Current density 2.2 A/dm
on a volume basis as follows:
Time 2 min
Liquids: as volume per litre of solution
7.6.1.2 Followed by Cathodic Treatment:
Solids: as mass per litre of solution
Current density 2.2 A/dm
7.3 The commercial grade acids and salts used in the
Time 6 min
formulas include: A
7.6.2 Nickel chloride 240 g
Sulfuric acid: 93 mass %; density 1.83 g/mL Hydrochloric acid 126 mL
Water to 1 L
Hydrochloric acid: 31 mass %; density 1.16 g/mL
Electrodes nickel
Nickel chloride: NiCl ·6H O B
2 2
Temperature room
Current density (cathodic) 5.4 to 21.5 A/dm
Copper sulfate: CuSO ·5H O
4 2
Time 2 to 4 min
A
NOTE 6—Precaution: Sulfuric acid should be slowly added to the See U. S. Patent No. 2,437,409.
B
Bath may require cooling or reduction in hydrochloric acid content if
approximate amount of water required with rapid mixing, and then after
temperature exceeds 30°C.
cooling, diluted to exact volume.
7.6.3 Nickel chloride 30 to 300 g/L
7.4 Cathodic Treatments: Hydrochloric acid 15 to 160 mL/L
Water to 1 L
B 254
9. Electroplating
Electrodes nickel
Temperature room
9.1 An adherent electrodeposit of commonly electroplated
Current density 0.55 to 10.75 A/dm
metals (cadmium, copper, brass, chromium, gold, nickel, or
Time ⁄2 to 5 min
7.6.4 Hydrochloric acid undiluted commercial grade
silver) may be electrodeposited directly on stainless steel
(7.2)
provided the surface of the stainless steel is active.
Copper sulfate 0.4 g/L
Electrodes nickel
NOTE 9—Nickel may be electrodeposited at normal current densities
Temperature room
2 directly on properly activated stainless steel from standard nickel-
Current density 4.5 to 6.6 A/dm
electroplating solutions if the pH of the solution is between 2 and 4. A pH
Time 1 to 5 min
of 2 is preferred.
NOTE 8—Nickel anode materials containing greater than 0.01 % sulfur
NOTE 10—When a chromium-electroplating solution containing 400
are not recommended for use in acid nickel strike baths operated at pH 0.5,
g/L of chromic acid is used for decorative chromium electroplating, better
or lower, to avoid oxidation of sulfides by hydrochloric acid (see section
coverage and a wider bright range is obtained by operating at a current
7.6.1, section 7.6.2, section 7.6.3, section 7.6.4, and 7.7). 2
density of 16.2 A/dm and 49°C.
NOTE 11—A bright nickel electroplate under chromium, preceded by
7.7 A combination of more than one type of treatment may
one of the simultaneous activation-electroplating treatments, may often be
be necessary to ensure a high degree of adhesion. For example,
used to advantage for better color matching and elimination of chromium
the following has been used in the automotive industry for
buffing.
nickel plating on UNS Type S30200 stainless steel:
9.2 Where practical, the parts should have the current
Sulfuric acid 650 mL
applied during entry into the electroplating solution.
Water to 1 L
Potential (cathodic) 10 V
10. Stripping
Electrodes lead
Temperature room
10.1 Nitric acid is the preferred stripping solution.
Time 2 min
10.2 Decorative chromium electrodeposits have been
Followed by:
stripped in a solution of 500 mL of concentrated, 31 mass %
Nickel chloride 240 g
hydrochloric acid (density 1.16 g/mL) diluted to 1 L at 45 to
Hydrochloric acid 120 mL
50°C for 1 min.
Water to 1 L
Electrodes nickel
NOTE 12—Overstripping will result in etching.
Temperature room
NOTE 13—Decorative chromium electrodeposits may also be stripped
Time 2 min
2 anodically in any alkaline solution.
Current density (cathodic) 16.2 A/dm
10.3 Cadmium is stripped successfully without current by
This is followed by transfer without rinsing to a Watts (or
immersion in a solution of 120 g/L of ammonium nitrate.
higher chloride) nickel bath with a pH of 1.5 to 2.0.
11. Post Electroplating Operations
8. Rinsing
11.1 Post electroplating operations such as stress relieving,
8.1 The parts should be transferred to the cold-water rinse
buffing or coloring, and forming or drawing may be applied to
and to the plating solution as rapidly as practicable after the
stainless steel in the same manner as to any other basis metal,
activating procedure; otherwise the surface will passivate itself
as long as the natural differences in the characteristic of the
and the electrodeposit will not be adherent.
stainless steel are taken into consideration. The stainless steel
8.1.1 The rinse water should be kept slightly acid (approxi-
supplier should be consulted for guidance in regard to these
mately pH of 2.5 to 3.5). The acid carryover from the activation
characteristics.
operation will maintain this pH in many instances.
12. Test Methods
8.1.2 In conveyorized operations where trace contamination
12.1 The methods of testing for thickness, hardness, and
of plating solutions with chloride and sulfate from activating
adhesion of electrodeposits applied with the usual basis metals
solutions will produce an unsatisfactory electrodeposit, spray-
may be employed for similar tests on stainless steel.
rinse operations subsequent to the activation treatment will
remove these contaminants.
NOTE 14—An exception to this is the determination of the thickness of
8.1.3 If the simultaneous activation-plating procedure is
chromium on stainless steel by the hydrochloric acid drop method.
Because gassing continues after the chromium coating has been pen-
employed and nickel plating follows, the intermediate rinse
etrated, the accuracy of this method may be questionable for this
need only be superficial and the length of transfer time is not
application.
so important.
B 254
APPENDIXES
(Nonmandatory Information)
X1
...
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