ASTM B242-99(2020)
(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 1) 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.
Note 1: 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 B183.
1.2 This guide does not apply to the electroplating of alloy steel. For methods of chromium electroplating directly on steel, see Guide B177.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For a specific hazards statement, see 3.1.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B242 − 99 (Reapproved 2020) Endorsed by American
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.
1. Scope 2. Referenced Documents
1.1 This guide is intended as an aid in establishing and
2.1 ASTM Standards:
maintaining a preparatory cycle for electroplating on high-
B177 Guide for Engineering Chromium Electroplating
carbon steel (Note 1) producing a minimum of hydrogen
B183 Practice for Preparation of Low-Carbon Steel for
embrittlement and maximum adhesion of the electrodeposited
Electroplating
metal. For the purpose of this guide, steels containing 0.35 %
B849 Specification for Pre-Treatments of Iron or Steel for
of carbon or more, and case-hardened low-carbon steel, are
Reducing Risk of Hydrogen Embrittlement
defined as high-carbon steels. There is no generally recognized
B850 Guide for Post-CoatingTreatments of Steel for Reduc-
definite carbon content dividing high from low-carbon steels
ing the Risk of Hydrogen Embrittlement
for electroplating purposes.
NOTE 1—Electroplating of plain high-carbon steel introduced problems 3. Reagents
not found in similar operations on low-carbon steel. During the cleaning
3.1 PurityofReagents—Allacidsandchemicalsusedinthis
andelectroplatingcycle,high-carbonsteeldiffersfromlow-carbonsteelin
regard to its greater tendency to become embrittled and the greater
practice are technical grade.Acid solutions are based upon the
difficulty in obtaining maximum adhesion of the electrodeposit. The
following assay materials:
preparation of low-carbon steel for electroplating is covered in Practice
Hydrochloric acid (HCl) 31 mass %, density 1.16 g/mL
B183.
Nitric acid (HNO ) 67 mass %, density 1.40 g/mL
1.2 This guide does not apply to the electroplating of alloy
Sulfuric acid (H SO ) 93 mass %, density 1.83 g/mL
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steel.Formethodsofchromiumelectroplatingdirectlyonsteel,
(Warning—Dilute sulfuric acid by slowly adding it to the
see Guide B177.
approximateamountofwaterrequiredwithrapidmixing.After
1.3 The values stated in SI units are to be regarded as
cooling, bring the mixture to exact volume.)
standard. No other units of measurement are included in this
standard. 3.2 Purity of Water—Use ordinary industrial or potable
water for preparing solutions and rinsing.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Nature of Steel
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4.1 Hardness—High hardness is a major cause of cracking
mine the applicability of regulatory limitations prior to use.
of the steel during or after electroplating. The recommended
For a specific hazards statement, see 3.1.
maximum hardness range for classes of products depends on
1.5 This international standard was developed in accor-
their geometry and service requirements (Note 2). Parts hard-
dance with internationally recognized principles on standard-
ened by heat treatment should be inspected before electroplat-
ization established in the Decision on Principles for the
ing for the presence of cracks by a suitable method, such as
Development of International Standards, Guides and Recom-
magnetic or fluorescent powder inspection.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
NOTE 2—Some examples of parts and Rockwell hardness ranges are as
follows:
This guide is under the jurisdiction of ASTM Committee B08 on Metallic and
Inorganic Coatings and is the direct responsibility of Subcommittee B08.02 on Pre
Treatment. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2020. Published December 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ε1
approved in 1949. Last previous edition approved in 2014 as B242 – 99(2014) . Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/B0242-99R20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B242 − 99 (2020)
5.1.7 Conditioning of the surface to be electroplated may be
Rockwell Hard-
ness Range
accomplished, where necessary for the electroplating process,
Springs C45 to C48
by a short dip or rinse in a solution equivalent to the
Spring washers C45 to C53
electroplating solution without its metallic content.
Small instrument parts C52 to C55
Parts to be chromium electroplated C57 to C62
5.2 Rinsing—Inadequate rinsing after each solution treat-
for engineering use
ment step is the recognized cause of a large portion of
4.2 Hydrogen Embrittlement—Difficulties resulting from
electroplating difficulties. Not enough rinsing is characteristic
hydrogen embrittlement increase with increasing hardness,
of most pretreatment cycles.
whether produced by heat treatment or cold work. Difficulties,
5.3 Pretreatment Time—All processing steps involving hy-
during or after electroplating of hardened high-carbon steel
parts, may in some cases be minimized without material drogen generation must be designed to operate for a minimum
length of time, to avoid hydrogen embrittlement of the high-
change in hardness by baking before final pretreatment. For a
listing of such hydrogen embrittlement relief bake cycles, carbon steel.
consult Guide B850.
5.4 Control—All pretreatment steps should be carried out
with solutions that are maintained in good working condition
4.3 Surface Oxidation—In order that subsequent treatments
by control of composition and contaminants, and used under
be facilitated, every reasonable precaution should be taken
conditions of time, temperature and current density specified to
throughouttheprocessingtolimitoxidationorscaleformation.
meet the requirement of the work being processed.
In particular cases pre-electroplating with copper to a mini-
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
recommended.
4.4 Steel Quality—The quality of the steel should be char-
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
imposed on the pretreatment cycle would impair its efficiency,
5.1 Preparatory Treatments—A wide variety of surface
increase its complexity, and tend to prevent the attainment of
conditions are encountered in high-carbon steel articles to be
the required quality of the deposit. The overall cost of the
electroplated. The surface may require the removal of one or
electroplating process is usually reduced by using the prelimi-
more of the following contaminants: grease, oil or drawing
nary treatments where applicable. Oil, grease, dirt, drawing
compounds, burned-in oil scale, light to heavy treatment scale,
compounds, burnt-in oil, heavy scale, and emery and steel
permeable oxide films, emery and fine steel particles resulting
particles are typical of the gross contaminants encountered.
fromthegrindingoperation.Theremovalofsuchcontaminants
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
quenching. 6.4 Mechanical Treatment—The purpose of mechanical
5.1.5 Smut removal by cyanide dipping or by anodic treat- treatment is to reduce subsequent acid pickling to a minimum.
ment in cyanide or alkali. Where mechanical treatment has been accomplished with
5.1.6 Final preparation for electroplating may be accom- precision, it is sometimes possible to eliminate acid pickling
plished by an anodic etching treatment in H SO (used when- entirely,thusimprovingthecontrolofhydrogenembrittlement.
2 4
ever possible in the interest of high yield and adhesion). When required, mechanical treatment of small parts is best
B242 − 99 (2020)
effected by tumbling. All scaled and nearly all oil-quenched the surface of the high-carbon steel. The intensity of the HCl
materials require mechanical cleaning such as by tumbling treatment should be held to the minimum required by the
with or without abrasive, or by sand, grit, or vapor blasting. nature and amount of oxide present. The use of H SO instead
2 4
These operations should be carried out so as to avoid severe of HCl is not recommended for descaling high-carbon steel
roughening of the surface with accompanying notch effect. because of its smut-forming tendency, in spite of the somewhat
One resorts to grinding in certain cases where the surface lowered tendency to rusting of H SO -treated surfaces. The
2 4
smoothness or dimensions of the parts are of critical addition of wetting agents to the HCl solution is not recom-
importance, for example, in chromium electroplating for engi- mended. Care and caution must be exercised in the use of
neering use. inhibitors where they are required, because they sometimes
interfere with adhesion. Inhibitors are of benefit only in special
cases where surface finish and dimensions are of prime
7. Final Pretreatment Procedures
importance.
7.1 Application—Final cleaning, oxide removal, and anodic
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
cyanide or alkaline treatment. Air-formed oxide, if not too
7.2 Electrolytic Anodic Cleaning:
heavy, can be removed by a cyanide dip after the rinse
7.2.1 All work, except work to be barrel electroplated,
following the acid treatment. A concentration of 22 g⁄L of
should preferably be cleaned in an electrolytic anodic alkaline
NaCN is sufficient for the cyanide dip. Where a severe smut
cleaner. Anodic cleaning is recommended to avoid hydrogen
condition exists, it can be eliminated by a ⁄2 to 1-min anodic
embrittlementthatislikelytoresultfromcathodiccleaning.An
treatment at 1.5 to 2 A/dm in a solution of a NaCN of the
exception is barrel work which, because of the work size, is
noncritical concentration of 45 g/L used at room temperature.
preferably cleaned by soaking or tumbling in an alkaline
An alternative treatment for a somewhat lighter smut condition
cleaning solution without the use of current.
is electrolytic anodic treatment in the noncyanide alkaline
7.2.2 The purpose of this cleaning step is to remove
cleaning solution (6.3) above 70 °C, for 15 to 30 s at 2.5 to
completelythelasttracesofcontaminants.Inallcasesitshould
5 A⁄dm . The current density is not critical.
be preceded by heavy-duty precleaning as covered in 6.2.
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
thoroughly rinsed, first with water warmed to 50 °C, and then
treatment is capable of removing a small amount of smut
inacold-watersprayatroomtemperature,priortotheaciddip.
formed by the preceding HCl treatment; more substantial
amounts of smut should be removed according to the proce-
7.3 Rinsing:
dures described in 7.5.
7.3.1 The most thorou
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