ASTM B254-92(2009)
(Practice)Standard Practice for Preparation of and Electroplating on Stainless Steel
Standard Practice for Preparation of and Electroplating on Stainless Steel
ABSTRACT
This practice covers the preparation and electroplating of metals on stainless steel. The preparation of stainless steel for electroplating involves three basic steps in the following order: removal of scale, removal of oil, grease, or other foreign material by cleaning, and activation immediately before electroplating. Activation shall be done by removing the thin transparent film of oxides from the surface to be electroplated. This film will reform if the parts are allowed to dry or are exposed to oxygen-containing solutions. For this reason, the shortest interval practicable should elapse between the time the parts are removed from the activating solution and covered by the electrodeposit, unless a simultaneous activation-electroplating procedure is used. The parts should be transferred to the cold-water rinse and to the plating solution as rapidly as practicable after the activating procedure; otherwise the surface will passivate itself and the electrodeposit will not be adherent. The rinse water should be kept slightly acid. After activation, an adherent electrodeposit of commonly electroplated metals like cadmium, copper, brass, chromium, gold, nickel, or silver may be electrodeposited directly on stainless steel provided the surface of the stainless steel. After stripping with nitric acid, post electroplating operations such as stress relieving, buffing or coloring, and forming or drawing may be applied to stainless steel in the same manner as to any other basis metal, as long as the natural differences in the characteristic of the stainless steel are taken into consideration. The methods of testing for thickness, hardness, and adhesion of electrodeposits applied with the usual basis metals may be employed for similar tests 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 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.
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Standards Content (Sample)
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Designation: B254 − 92(Reapproved 2009) Endorsed by American
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 B254; 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.
1. Scope of the stainless steel with which he is working before outlining
his electrodeposition procedure (see Appendix X1).
1.1 Various metals are electrodeposited on stainless steel for
color matching, lubrication during cold heading, spring-coiling
3.2 Stainless steel surfaces are normally resistant to a wide
and wire-drawing operations, reduction of scaling at high
variety of corrosive elements. This property is the result of a
temperatures,improvementofwettability(asinfountainpens),
thin transparent film of oxides present on the surface. Because
improvement of heat and electrical conductance, prevention of
this film rapidly reforms after it has been stripped off or
galling, jewelry decoration, and prevention of superficial
penetrated, it protects stainless steel against corrosion. An
rusting.
adherent electrodeposit cannot be obtained over the oxide film
normally present on stainless steel. However, once this film is
1.2 This practice is presented as an aid to electroplaters and
removed by surface activation and kept from reforming while
finishing engineers, confronted with problems inherent in the
the surface is covered with an electrodeposit, any of the
electrodeposition of metals on stainless steel. It is not a
commonly electroplated metals may be electrodeposited suc-
standardizedprocedurebutaguidetotheproductionofsmooth
cessfully on stainless steel.
adherent electrodeposits on stainless steel.
3.3 Where the finished product is to be subjected to severe
1.3 This standard does not purport to address all of the
exposure, the deposit produced by the proposed electroplating
safety concerns, if any, associated with its use. It is the
sequence should be tested under similar exposure conditions
responsibility of the user of this standard to establish appro-
before adoption, to determine whether the natural corrosion
priate safety and health practices and determine the applica-
resistance of the stainless steel has been impaired by the
bility of regulatory limitations prior to use.
presence of the electrodeposit.
2. Referenced Documents
2 4. Nature of Cleaning
2.1 ASTM Standards:
A380 Practice for Cleaning, Descaling, and Passivation of
4.1 The preparation of stainless steel for electroplating
Stainless Steel Parts, Equipment, and Systems
involves three basic steps in the following order:
4.1.1 Removalofscale.Ifscaleremovalisnecessary,oneof
3. Nature of Stainless Steel
the methods outlined in Appendix X2 may be used (Note 1).
See also Practice A380.
3.1 Because previous metal treatment may have a more
4.1.2 Removal of oil, grease, or other foreign material by
pronounced effect on the final finish when stainless steel is
cleaning, and
being electroplated, the metal finisher should become ac-
quainted with the fabrication procedure, grade, and mill finish 4.1.3 Activation immediately before electroplating.
4.2 Precleaning—Removal of fabricating lubricants and
finishing compounds from the stainless steel may have to be
This practice is under the jurisdiction of ASTM Committee B08 on Metallic
undertaken immediately following the fabrication or finishing
and Inorganic Coatingsand is the direct responsibility of Subcommittee B08.02 on
operation (Note 2).
Pre Treatment.
Current edition approved Sept. 1, 2009. Published December 2009. Originally
4.3 Electrocleaning—Anodiccleaningisgenerallypreferred
ε1
approved in 1951. Last previous edition approved in 2004 as B254–92 (2004) .
(Note 3).
DOI: 10.1520/B0254-92R09.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4.4 Metal Lubricants—Metal lubricants such as copper,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
lead, or cadmium, applied to stainless steel wire for cold
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. heading, wire drawing, or spring forming are removed by
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B254 − 92 (2009)
immersioninasolutionof200mLofconcentrated,67mass %, Hydrochloric acid: 31 mass %; density 1.16 g/mL
nitricacid(density1.40g/mL)dilutedto1Lat50to60°C.See Nickel chloride: NiCl ·6H O
2 2
Practice A380.
Copper sulfate: CuSO ·5H O
4 2
Warning—Sulfuric acid should be slowly added to the
NOTE 1—Oil, grease or other fabricating lubricants should be removed
by cleaning before heat treating.
approximate amount of water required with rapid mixing, and
NOTE 2—Spray cleaning with a nozzle pressure of 200 to 400 kPa (30
then after cooling, diluted to exact volume.
to 60 psi) in a power washer, using an alkaline or emulsion-type cleaner,
is the generally preferred method, especially for the removal of heavy
7.4 Cathodic Treatments:
drawing, buffing, or polishing compounds. Soak cleaning or vapor
7.4.1 Sulfuric acid 50 to 500 mL/L
degreasing may also be used. Extreme examples of such compounds are
Water to1L
drawing or stamping lubricants containing unsaturated oils, which if left
Temperature room
on the surface, form by air-oxidation tenacious films that are very difficult
Time 1to5min
to remove. 2
Current density 0.54 A/dm
NOTE 3—When brightness is important, alkalinity, current density, and
Anodes pure lead
A
temperature should be kept as low as the part will permit. This is an
7.4.2 Hydrochloric acid 50 to 500 mL/L
essential requirement when cleaning work on racks bearing auxiliary lead Water to1L
Temperature room
anodes or when high chromium alloys (such as UNS Types S44200 and
Time 1to5min
S44600) are being cleaned.
Current density 2.15 A/dm
Anodes electrolytic nickel strip or nickel
5. Cleaning Solutions
bar
A
See Patent No. 2,133,996.
5.1 The types of solution control, electrodes, heating coils,
7.4.3 After immersion in a solution containing 100 to 300 mL/L of
and rinse tanks normally used for cleaning carbon steel are
hydrochloric acid diluted to 1 L at room temperature for 30 to 60 s, treat
satisfactory for stainless steel. Equipment previously used for cathodically in:
Sulfuric acid 50 to 500 mL/L
the cleaning or processing of carbon steel should not be used.
Water to1L
See Practice A380.
Temperature room
Current 0.54 to 2.7 A/dm
Anodes pure lead
6. Racking
6.1 The general principles of good racking as used in 7.5 Immersion Treatments:
chromium electroplating processes apply. However, the high
7.5.1 Immerse in a solution of sulfuric acid containing 200
electrical resistance of stainless steel requires rack construction
to 500 mLof acid diluted to 1 Lat 65 to 80°C (with the higher
methods that minimize potential contact problems and increase
temperature for the lower concentration) for at least 1 min after
the number of contact points.
gassing starts. If gassing does not start within 1 min after the
parts have been immersed, touch them with a carbon-steel bar
NOTE 4—Because of the high electrical resistance of stainless steel,
especiallyinfine-coiledwirearticlessuchaswatchbands,chains,jewelry,
or rod. This activation treatment will produce a dark, adherent
etc., it is necessary to provide a larger number of contacts.As an example,
smut that is removed in the electroplating bath. A cathodic
a watch band 110 mm long made of 1.0-mm diameter wire has been found
current of at least 0.54 A/dm may be used to accelerate
to require at least three contacts.
activation. Lead anodes are suitable for this solution.
7. Activation
7.5.2 Immerse in the following solution:
7.1 After the cleaning operation and before the electroplat- Hydrochloric acid 1 mL
Sulfuric acid 10 mL
ing operation, the parts must be completely activated, that is,
Water to1L
the thin transparent film of oxides must be removed from the
Temperature room
surfacetobeelectroplated(Note5).Thisfilmwillreformifthe Time 26 s
parts are allowed to dry or are exposed to oxygen-containing
NOTE 6—This practice has been used with success for chromium
solutions. For this reason, the shortest interval practicable
electroplating on stainless steel automobile parts in a conveyorized
should elapse between the time the parts are removed from the
process. It is not recommended before copper or nickel electroplating.
activating solution and covered by the electrodeposit, unless a
7.6 Simultaneous Activation-Electroplating Treatments:
simultaneous activation-electroplating procedure is used.
A
7.6.1 Nickel chloride 240 g
NOTE 5—The etching practice may be more severe for nondecorative
Hydrochloric acid 85 mL
applications than for decorative applications.
Iron should not exceed
7.5 g/L
7.2 The following activating procedures have been used.
Water to1L
The procedure selected will depend upon the nature of the part
Temperature room
Electrodes nickel
and preceding or subsequent processes (see 7.7). In the
A
See U. S. Patent No. 2,285,548-9.
following solution formulas, the concentrations are expressed
7.6.1.1 Anodic Treatment:
on a volume basis as follows:
Liquids: as volume per litre of solution
Current density 2.2 A/dm
Time 2 min
Solids: as mass per litre of solution
7.6.1.2 Followed by Cathodic Treatment:
7.3 The commercial grade acids and salts used in the
Current density 2.2 A/dm
formulas include:
Time 6 min
Sulfuric acid: 93 mass %; density 1.83 g/mL
B254 − 92 (2009)
A
8.1.3 If the simultaneous activation-plating procedure is
7.6.2 Nickel chloride 240 g
Hydrochloric acid 126 mL
employed and nickel plating follows, the intermediate rinse
Water to1L
need only be superficial and the length of transfer time is not
Electrodes nickel
B
so important.
Temperature room
Current density (cathodic) 5.4 to 21.5 A/dm
Time 2to4min 9. Electroplating
A
See U. S. Patent No. 2,437,409.
B
9.1 An adherent electrodeposit of commonly electroplated
Bath may require cooling or reduction in hydrochloric acid content if
temperature exceeds 30°C.
metals (cadmium, copper, brass, chromium, gold, nickel, or
7.6.3 Nickel chloride 30 to 300 g/L
silver) may be electrodeposited directly on stainless steel
Hydrochloric acid 15 to 160 mL/L
provided the surface of the stainless steel is active.
Water to1L
Electrodes nickel
NOTE 8—Nickel may be electrodeposited at normal current densities
Temperature room
directly on properly activated stainless steel from standard nickel-
Current density 0.55 to 10.75 A/dm
electroplating solutions if the pH of the solution is between 2 and 4.ApH
Time ⁄2 to5min
of 2 is preferred.
7.6.4 Hydrochloric acid undiluted commercial grade
NOTE 9—When a chromium-electroplating solution containing 400 g/L
(7.2)
Copper sulfate 0.4 g/L of chromic acid is used for decorative chromium electroplating, better
Electrodes nickel
coverage and a wider bright range is obtained by operating at a current
Temperature room
density of 16.2 A/dm and 49°C.
Current density 4.5 to 6.6 A/dm
NOTE 10—A bright nickel electroplate under chromium, preceded by
Time 1to5min
one of the simultaneous activation-electroplating treatments, may often be
used to advantage for better color matching and elimination of chromium
NOTE 7—Nickel anode materials containing greater than 0.01 % sulfur
buffing.
arenotrecommendedforuseinacidnickelstrikebathsoperatedatpH0.5,
or lower, to avoid oxidation of sulfides by hydrochloric acid (see
9.2 Where practical, the parts should have the current
7.6.1-7.6.4, and 7.7).
applied during entry into the electroplating solution.
7.7 A combination of more than one type of treatment may
10. Stripping
be necessary to ensure a high degree of adhesion. For example,
the following has been used in the automotive industry for
10.1 Nitric acid is the preferred stripping solution.
nickel plating on UNS Type S30200 stainless steel:
10.2 Decorative chromium electrodeposits have been
Sulfuric acid 650 mL
stripped in a solution of 500 mL of concentrated, 31 mass %
Water to1L
hydrochloric acid (density 1.16 g/mL) diluted to 1 L at 45 to
Potential (cathodic) 10 V
Electrodes lead
50°C for 1 min.
Temperature room
Time 2 min
NOTE 11—Overstripping will result in etching.
NOTE 12—Decorative chromium electrodeposits may also be stripped
Followed by:
anodically in any alkaline solution.
Nickel chloride 240 g
10.3 Cadmium is stripped successfully without current by
Hydrochloric acid 120 mL
Water to1L
immersion in a solution of 120 g/L of ammonium nitrate.
Electrodes nickel
Temperature room
11. Post Electroplating Operations
Time 2 min
Current density (cathodic) 16.2 A/dm
11.1 Post electroplating operations such as stress relieving,
This is followed by transfer without rinsing to a Watts (or
buffing or coloring, and forming or drawing may be applied to
higher chloride) nickel bath with a pH of 1.5 to 2.0.
stainless steel in the same manner as to any other basis metal,
as long as the natural differences in the characteristic of the
8. Rinsing
stainless steel are taken into consideration. The stainless steel
8.1 The parts should be transferred to the cold-water rinse
supplier should be consulted for guidance in regard to these
and to the plating solution as rapidly as practicable after the
characteristics.
activating procedure; otherwise the surface will passivate itself
12. Test Methods
and the electrodeposit will not be adherent.
8.1.1 The rinse water should be kept slightly acid (approxi-
12.1 The methods of testing for thickness, hardness, and
matelypHof2.5to3.5).Theacidcarryoverfromtheactivation
adhesion of electrodeposits applied with the usual basis metals
operation will maintain this pH in many instances.
may be employed for similar tests on stainless steel.
8.1.2 In conveyorized operations where trace contamination
NOTE 13—An exception to this is the determination of the thickness of
of plating solutions with chloride and sulfate from activating
chromium on stainless steel by the hydrochloric acid drop method.
solutions will produce an unsatisfactory electrodeposit, spray-
Because gassing continues after the chromium coating has been
rinse operations subsequent to the activation treatment will
penetrated, the accuracy of this method may be questionable for this
remove these contaminants. application.
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