ASTM B242-99(2004)e1
(Guide)Standard Guide for Preparation of High-Carbon Steel for Electroplating
Standard Guide for Preparation of High-Carbon Steel for Electroplating
ABSTRACT
This guide outlines the standard procedure for establishing and maintaining a preparatory cycle for electroplating on high carbon steel producing minimal hydrogen embrittlement and maximal adhesion of the electrodeposited metal. The reagents needed for this method are technical grade hydrochloric acid, nitric acid, sulfuric acid, and water. Steel substrates shall conform to required hardness, hydrogen embrittlement, and surface oxidation characteristics, and quality. Proper preplating treatments such as precleaning, stress relief treatment, mechanical treatment, electrolytic anodic cleaning, hydrochloric acid treatment, treatment for smut removal, anodic acid etching, and electropolishing shall be performed. Coating adhesion and embrittlement shall be tested.
SCOPE
1.1 This guide is intended as an aid in establishing and maintaining a preparatory cycle for electroplating on high-carbon steel (Note 0) producing a minimum of hydrogen embrittlement and maximum adhesion of the electrodeposited metal. For the purpose of this guide, steels containing 0.35 % of carbon or more, and case-hardened low-carbon steel, are defined as high-carbon steels. There is no generally recognized definite carbon content dividing high from low-carbon steels for electroplating purposes. Electroplating of plain high-carbon steel introduced problems not found in similar operations on low-carbon steel. During the cleaning and electroplating cycle, high-carbon steel differs from low-carbon steel in regard to its greater tendency to become embrittled and the greater difficulty in obtaining maximum adhesion of the electrodeposit. The preparation of low-carbon steel for electroplating is covered in Practice B 183.
1.2 This guide does not apply to the electroplating of alloy steel. For methods of chromium electroplating directly on steel see Guide B 177.
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 hazards statement, see .
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Endorsed by American
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Designation:B242–99(Reapproved 2004) Electroplaters’ Society
Endorsed by National
Association of Metal Finishers
Standard Guide for
Preparation of High-Carbon Steel for Electroplating
This standard is issued under the fixed designation B242; 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.
´ NOTE—The Warning note in Section 3.1 was editorially updated in October 2004.
1. Scope B183 Practice for Preparation of Low-Carbon Steel for
Electroplating
1.1 This guide is intended as an aid in establishing and
B849 Specification for Pre-Treatments of Iron or Steel for
maintaining a preparatory cycle for electroplating on high-
Reducing Risk of Hydrogen Embrittlement
carbon steel (Note 1) producing a minimum of hydrogen
B850 Guide for Post-Coating Treatments of Steel for Re-
embrittlement and maximum adhesion of the electrodeposited
ducing the Risk of Hydrogen Embrittlement
metal. For the purpose of this guide, steels containing 0.35 %
of carbon or more, and case-hardened low-carbon steel, are
3. Reagents
defined as high-carbon steels. There is no generally recognized
3.1 Purity of Reagents—All acids and chemicals used in
definite carbon content dividing high from low-carbon steels
this practice are technical grade.Acid solutions are based upon
for electroplating purposes.
the following assay materials:
NOTE 1—Electroplating of plain high-carbon steel introduced problems
not found in similar operations on low-carbon steel. During the cleaning
Hydrochloric acid (HCl) 31 mass %, density 1.16 g/mL
andelectroplatingcycle,high-carbonsteeldiffersfromlow-carbonsteelin
Nitric acid (HNO ) 67 mass %, density 1.40 g/mL
regard to its greater tendency to become embrittled and the greater
Sulfuric acid (H SO ) 93 mass %, density 1.83 g/mL
2 4
difficulty in obtaining maximum adhesion of the electrodeposit. The
(Warning—Dilute sulfuric acid by slowly adding it to the
preparation of low-carbon steel for electroplating is covered in Practice
B183. approximateamountofwaterrequiredwithrapidmixing.After
cooling, bring the mixture to exact volume.)
1.2 This guide does not apply to the electroplating of alloy
3.2 Purity of Water—Use ordinary industrial or potable
steel. For methods of chromium electroplating directly on steel
water for preparing solutions and rinsing.
see Guide B177.
1.3 This standard does not purport to address all of the
4. Nature of Steel
safety problems associated with its use. It is the responsibility
4.1 Hardness—High hardness is a major cause of cracking
of the user of this standard to establish appropriate safety and
of the steel during or after electroplating. The recommended
health practices and determine the applicability of regulatory
maximum hardness range for classes of products depends on
limitations prior to use. For a specific hazards statement, see
their geometry and service requirements (Note 2). Parts hard-
3.1.
ened by heat treatment should be inspected before electroplat-
2. Referenced Documents ing for the presence of cracks by a suitable method, such as
2 magnetic or fluorescent powder inspection.
2.1 ASTM Standards:
B177 Guide for Engineering Chromium Electroplating
NOTE 2—Some examples of parts and Rockwell hardness ranges are as
follows:
Rockwell Hard-
This guide is under the jurisdiction of ASTM Committee B08 on Metallic and
ness Range
Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on Pre
Springs C45 to C48
Treatment. Spring washers C45 to C53
Current edition approved Oct. 1, 2004. Published October 2004. Originally Small instrument parts C52 to C55
Parts to be chromium electroplated C57 to C62
approved in 1949. Last previous edition approved in 1999 as B242 – 99. DOI:
for engineering use
10.1520/B0242-99R04E01.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4.2 Hydrogen Embrittlement—Difficulties resulting from
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
hydrogen embrittlement increase with increasing hardness,
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. whether produced by heat treatment or cold work. Difficulties,
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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B242–99 (2004)
during or after electroplating of hardened high-carbon steel 5.3 Pretreatment Time—All processing steps involving hy-
parts, may in some cases be minimized without material drogen generation must be designed to operate for a minimum
change in hardness by baking before final pretreatment. For a
length of time, to avoid hydrogen embrittlement of the high-
listing of such hydrogen embrittlement relief bake cycles, carbon steel.
consult Guide B850.
5.4 Control—All pretreatment steps should be carried out
4.3 Surface Oxidation—In order that subsequent treatments
with solutions that are maintained in good working condition
be facilitated, every reasonable precaution should be taken
by control of composition and contaminants, and used under
throughouttheprocessingtolimitoxidationorscaleformation.
conditions of time, temperature and current density specified to
In particular cases pre-electroplating with copper to a mini-
meet the requirement of the work being processed.
mum thickness of 13 µm may assist in maintaining a preferred
5.5 Pretreatment Cycle Design—Depending upon the re-
surface through the heat treatment.Anonoxidizing atmosphere
quirements for the particular high-carbon steel parts to be
should be maintained in the furnace. This copper shall be
electroplated, a minimum cycle should be selected from the
removed prior to the regular electroplating cycle. Care should
generalstepslistedin5.1.Differentclassesofmaterialsrequire
be used in oil-quenching parts heat treated in a salt bath, to
selected process steps combined into pretreatment cycles of
prevent the charring effect that can be caused by salt-bath
greater or less complexity according to the condition and
drag-out. Proper lead-bath quenching results in only slight
properties of the material. The minimum number of steps
oxidation.
necessary to accomplish the electroplating satisfactorily is
4.4 Steel Quality—The quality of the steel should be char-
recommended.
acteristic of the requirement of the product and the electroplat-
ing operation. The steel should be free of injurious surface
6. Preliminary Pretreatment Procedures
defects, and of at least average cleanliness.
6.1 Application—Degreasing and mechanical surface treat-
ment are necessary only where the high-carbon steel parts are
5. Preparation of Steel, General
contaminated to such an extent that otherwise the burden
5.1 Preparatory Treatments—A wide variety of surface
imposed on the pretreatment cycle would impair its efficiency,
conditions are encountered in high-carbon steel articles to be
increase its complexity, and tend to prevent the attainment of
electroplated. The surface may require the removal of one or
the required quality of the deposit. The overall cost of the
more of the following contaminants: grease, oil or drawing
electroplating process is usually reduced by using the prelimi-
compounds, burned-in oil scale, light to heavy treatment scale,
nary treatments where applicable. Oil, grease, dirt, drawing
permeable oxide films, emery and fine steel particles resulting
compounds, burnt-in oil, heavy scale, and emery and steel
fromthegrindingoperation.Theremovalofsuchcontaminants
particles are typical of the gross contaminants encountered.
is accomplished by one or more of the following pretreatment
6.2 Precleaning—Solvent-degreasing with clean solvent,
procedures where applicable:
spray-washing, or emulsion-cleaning, followed by electrolytic
5.1.1 Substantial removal of oil, grease, and caked-on dirt
or soak-alkali cleaners are recommended.The former types are
by precleaning before the part enters the electroplating cycle
preferred to reduce the burden on the alkali treatments.
(applicable in all cases).
Soak-alkali cleaning is usual for parts that are to be barrel
5.1.2 Mechanical treatment of the surface by tumbling, sand
electroplated. Electrolytic cleaning should always be anodic
or grit blasting, vapor blasting, or grinding (optional).
where the control of embrittlement is a problem.
5.1.3 Final and complete anodic cleaning in an electrolytic
6.3 Stress Relief Treatment—It is recommended that hard-
alkali cleaner.
ened high-carbon steel parts receive a stress-relief bake before
5.1.4 AcidtreatmentinHCltoremovethelasttraceofoxide
the parts are mechanically pretreated or enter the final pretreat-
and scale. This should be avoided for spring temper and
ment cycle, or both. For a listing of typical stress-relief bakes,
case-hardened parts. This treatment also removes residual
consult Specification B849.
traces of lead that may be present following proper lead-bath
6.4 Mechanical Treatment—The purpose of mechanical
quenching.
treatment is to reduce subsequent acid pickling to a minimum.
5.1.5 Smut removal by cyanide dipping or by anodic treat-
Where mechanical treatment has been accomplished with
ment in cyanide or alkali.
precision, it is sometimes possible to eliminate acid pickling
5.1.6 Final preparation for electroplating may be accom-
entirely,thusimprovingthecontrolofhydrogenembrittlement.
plished by an anodic etching treatment in H SO (used when-
2 4 When required, mechanical treatment of small parts is best
ever possible in the interest of high yield and adhesion).
effected by tumbling. All scaled and nearly all oil-quenched
5.1.7 Conditioning of the surface to be electroplated may be
materials require mechanical cleaning such as by tumbling
accomplished, where necessary for the electroplating process,
with or without abrasive, or by sand, grit, or vapor blasting.
by a short dip or rinse in a solution equivalent to the
These operations should be carried out so as to avoid severe
electroplating solution without its metallic content.
roughening of the surface with accompanying notch effect.
One resorts to grinding in certain cases where the surface
5.2 Rinsing—Inadequate rinsing after each solution treat-
ment step is the recognized cause of a large portion of smoothness or dimensions of the parts are of critical impor-
tance, for example, in chromium electroplating for engineering
electroplating difficulties. Not enough rinsing is characteristic
of most pretreatment cycles. use.
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B242–99 (2004)
7. Final Pretreatment Procedures interfere with adhesion. Inhibitors are of benefit only in special
cases where surface finish and dimensions are of prime
7.1 Application—Final cleaning, oxide removal, and anodic
importance.
acid treatment are fundamental steps required for preparing
7.5 Treatment for Smut Removal—When the HCl treatment
high-carbon steel for electroplating. These pretreatment steps
of the high-carbon steel results in the presence of smut, the
are designed to assist in the control of hydrogen embrittlement
smut must be removed before the surface is electroplated.
and in securing the maximum adhesion of the electroplated
Light oxides formed on exposure to air after acid treatment
coating.
must likewise be removed. This can be done by an anodic
7.2 Electrolytic Anodic Cleaning:
cyanide or alkaline treatment. Air-formed oxide, if not too
7.2.1 All work, except work to be barrel electroplated,
heavy, can be removed by a cyanide dip after the rinse
should preferably be cleaned in an electrolytic anodic alkaline
following the acid treatment. A concentration of 22 g/L of
cleaner. Anodic cleaning is recommended to avoid hydrogen
NaCN is sufficient for the cyanide dip. Where a severe smut
embrittlementthatislikelytoresultfromcathodiccleaning.An
condition exists, it can be eliminated by a ⁄2 to 1-min anodic
exception is barrel work which, because of the work size, is
treatment at 1.5 to 2 A/dm in a solution of a NaCN of the
preferably cleaned by soaking or tumbling in an alkaline
noncritical concentration of 45 g/L used at room temperature.
cleaning solution without the use of current.
An alternative treatment for a somewhat lighter smut condition
7.2.2 The purpose of this cleaning step is to remove
is electrolytic anodic treatment in the noncyanide alkaline
completelythelasttracesofcontaminants.Inallcasesitshould
cleaning solution (6.3) above 70°C, for 15 to 30 s at 2.5 to 5
be preceded by heavy-duty precleaning as covered in 6.2.
A/dm . The current density is not critical.
7.2.3 The electrolytic anodic cleaner should be used at a
7.6 Anodic Acid Etching:
temperature of 90°C or higher, and at a current density of 5
7.6.1 The use of an anodic acid etch and subsequent rinse as
A/dm or higher, in order that the required degree of cleanli-
final steps in the preparation for electroplating of high-carbon
ness be obtained in a time period not exceeding 2 min.
steel is of importance in securing adhesion. Without such an
7.2.4 On removal from the cleaner, the work should be
anodic treatment, poor adhesion may occur. The anodic acid
thoroughlyrinsed,firstwithwaterwarmedto50°C,andthenin
treatment is capable of removing a small amount of smut
a cold-water spray at room temperature, prior to the acid dip.
formed by the preceding HCl treatment; more substantial
7.3 Rinsing:
amounts of smut should be removed according to the proce-
7.3.1 The most thorough fresh-water rinsing operation pos-
dures described in 6.5.
sible is mandatory after each processing step if the best results
7.6.2 A150 to 600 mL/L H SO solution used at a tempera-
2 4
in electroplating high-carbon steel are to be obtained. The
ture of not more than 30°C, and preferably below 25°C, is
purpose of rinsing is to eliminate drag-over by complete
effective for anodic etching of high-carbon steel. SeeWarning
removaloftheprecedingsolutionfromthesurfaceofthework.
in 3.1. The addition of 125 g/L of Na SO (based on the
2 4
Many existing commercial operations are characterized by
anhydrous salt) is of benefit for many steel grades. Anodic
inadequate rinsing.
treatment in this solution for a time usually not exceeding 1
7.3.2 Warm to hot rinses should be used following alkaline
2 2
min at a current density of 16A/dm (range of 10 to 43A/dm )
solutions or where the subsequent processing solution is hot.
is sufficient.Ahigh acid content, high current density, and low
Therinsetemperatureshouldnotbesohighastoinducedrying
temperature (with reference to the ranges specified) will
of the steel surface bet
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