ASTM B177/B177M-11(2021)
(Guide)Standard Guide for Engineering Chromium Electroplating
Standard Guide for Engineering Chromium Electroplating
ABSTRACT
This guide provides information on the deposition of engineering chromium by electroplating. This is sometimes called "functional" or "hard" chromium and is usually applied directly to the basis metal and is usually thicker than decorative deposits. This guide is not intended as a standardized procedure, but as a guide for obtaining smooth, adherent coatings of a desired thickness while retaining the required physical and mechanical properties of the base metals. Engineering chromium may be plated directly to the surface of a commonly used engineering metals such as aluminum, nickel alloys, cast iron, steels, copper, copper alloys, and titanium. Substrate requirements including smoothness, fatigue, high-strength steel stress relief, and oxidation are specified. The procedure and requirements for the following are detailed: (1) racking, including rack and anode designs, (2) cleaning, (3) deoxidizing and etching such as anodic etching in chromic acid solution, in plating solution, and in sulfuric acid solution, and slight etching by acid immersion, (4) chromium electroplating process, (5) treatment of chromium coatings such as baking to avoid hydrogen embrittlement, and mechanical finishing by grinding, grinding and honing, or lapping, (6) repair of chromium electrodeposits on steel substrates, and (7) test methods such as thickness determination, hardness test, and adhesion test.
SCOPE
1.1 This guide provides information about the deposition of chromium on steel for engineering uses. This is sometimes called “functional” or “hard” chromium and is usually applied directly to the basis metal and is usually thicker than decorative deposits.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.3 This guide is not intended as a standardized procedure, but as a guide for obtaining smooth, adherent coatings of chromium of a desired thickness while retaining the required physical and mechanical properties of the base metals. Specified chromium electrodeposits on ferrous surfaces are defined in Specification B650.
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.
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
Relations
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: B177/B177M − 11 (Reapproved 2021) Endorsed by American
Electroplaters’ Society
Endorsed by National
Association of Metal Finishers
Standard Guide for
Engineering Chromium Electroplating
This standard is issued under the fixed designation B177/B177M; 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 2. Referenced Documents
1.1 This guide provides information about the deposition of 2.1 ASTM Standards:
chromium on steel for engineering uses. This is sometimes B183 Practice for Preparation of Low-Carbon Steel for
called “functional” or “hard” chromium and is usually applied Electroplating
directlytothebasismetalandisusuallythickerthandecorative B242 Guide for Preparation of High-Carbon Steel for Elec-
deposits. troplating
B244 Test Method for Measurement of Thickness ofAnodic
1.2 The values stated in either SI units or inch-pound units
Coatings on Aluminum and of Other Nonconductive
are to be regarded separately as standard. The values stated in
Coatings on Nonmagnetic Basis Metals with Eddy-
each system may not be exact equivalents; therefore, each
Current Instruments
system shall be used independently of the other. Combining
B253 Guide for Preparation of Aluminum Alloys for Elec-
values from the two systems may result in non-conformance
troplating
with the standard.
B254 Practice for Preparation of and Electroplating on
1.3 This guide is not intended as a standardized procedure,
Stainless Steel
but as a guide for obtaining smooth, adherent coatings of
B281 Practice for Preparation of Copper and Copper-Base
chromium of a desired thickness while retaining the required
Alloys for Electroplating and Conversion Coatings
physical and mechanical properties of the base metals. Speci-
B320 Practice for Preparation of Iron Castings for Electro-
fied chromium electrodeposits on ferrous surfaces are defined
plating
in Specification B650.
B322 Guide for Cleaning Metals Prior to Electroplating
1.4 This standard does not purport to address all of the
B481 Practice for Preparation of Titanium and Titanium
safety concerns, if any, associated with its use. It is the Alloys for Electroplating
responsibility of the user of this standard to establish appro-
B487 Test Method for Measurement of Metal and Oxide
priate safety, health, and environmental practices and deter- Coating Thickness by Microscopical Examination of
mine the applicability of regulatory limitations prior to use.
Cross Section
1.5 This international standard was developed in accor- B499 Test Method for Measurement of Coating Thicknesses
dance with internationally recognized principles on standard-
by the Magnetic Method: Nonmagnetic Coatings on
ization established in the Decision on Principles for the Magnetic Basis Metals
Development of International Standards, Guides and Recom-
B504 Test Method for Measurement of Thickness of Metal-
mendations issued by the World Trade Organization Technical lic Coatings by the Coulometric Method
Barriers to Trade (TBT) Committee.
B507 Practice for Design of Articles to Be Electroplated on
Racks
This guide is under the jurisdiction of ASTM Committee B08 on Metallic and
Inorganic Coatings and is the direct responsibility of Subcommittee B08.03 on
Engineering Coatings. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2021. Published October 2021. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1955. Last previous edition approved in 2017 as B177/B177M – 11 Standards volume information, refer to the standard’s Document Summary page on
(2017). DOI: 10.1520/B0177_B0177M-11R21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B177/B177M − 11 (2021)
B558 Practice for Preparation of Nickel Alloys for Electro- bath chemistry or the plating conditions, or both, or as a result
plating of grinding of the electrodeposit can lead to a reduction in the
B568 Test Method for Measurement of Coating Thickness fatigue life of the electroplated part. If this is a design
by X-Ray Spectrometry consideration, the use of mechanical methods such as shot
B571 Practice for Qualitative Adhesion Testing of Metallic peening (see Specification B851 or MIL-S-13165C, or both) or
Coatings autofrettage to compressively stress the surface can increase
B578 Test Method for Microhardness of Electroplated Coat- the fatigue strength. This should be done after any stress-
ings relieving heat treatment.
B602 Test Method for Attribute Sampling of Metallic and
3.4 High-Strength Steel Stress Relief:
Inorganic Coatings
3.4.1 All steel parts having an ultimate tensile strength of
B630 Practice for Preparation of Chromium for Electroplat-
1000 MPa [150 000 psi, approximately 32 HRC] or greater,
ing with Chromium
which may contain residual stress caused by various fabrica-
B650 Specification for Electrodeposited Engineering Chro-
tion operations such as machining, grinding, straightening, or
mium Coatings on Ferrous Substrates
cold-forming, usually will require one of the stress relief bakes
B697 Guide for Selection of Sampling Plans for Inspection
prescribed in Specification B849 prior to electroplating. In all
of Electrodeposited Metallic and Inorganic Coatings
cases, the duration of the bake shall commence from the time
B762 Test Method of Variables Sampling of Metallic and
at which the whole of each part attains the specified tempera-
Inorganic Coatings
ture. This stress relief is essential if hydrogen embrittlement
B849 Specification for Pre-Treatments of Iron or Steel for
from subsequent operations is to be avoided.
Reducing Risk of Hydrogen Embrittlement
3.4.2 Parts having surface-hardened areas that would suffer
B850 Guide for Post-CoatingTreatments of Steel for Reduc-
an unacceptable reduction in hardness by baking in accordance
ing the Risk of Hydrogen Embrittlement
with Specification B849 may be baked at a lower temperature
B851 Specification for Automated Controlled Shot Peening
but not less than 130°C for a minimum period of 8 h. Shorter
of Metallic Articles Prior to Nickel, Autocatalytic Nickel,
times at higher temperatures may be used, if the resulting loss
or Chromium Plating, or as Final Finish
in surface hardness is acceptable.
F519 Test Method for Mechanical Hydrogen Embrittlement
3.5 Oxidation—All possible precautions should be taken to
Evaluation of Plating/Coating Processes and Service En-
prevent oxidation of the metal surface between the final
vironments
operations of mechanical preparation and electroplating, par-
2.2 Military Standard:
ticularly with steel substrates. Materials such as aluminum and
MIL-S-13165B Shot Peening of Metal Parts
titanium have an inherent oxide film on the surface that can
only be removed or minimized just prior to the electroplating
3. Substrates
process (see 6.1.1 and 6.1.2). When conditions are especially
3.1 Engineering chromium may be plated directly to the
unfavorable,definitestepsmustbetakentomeetthisimportant
surface of a number of commonly used engineering metals
requirement, including storage in a noncorrosive environment,
such as aluminum, nickel alloys, cast iron, steels, copper,
or the use of a suitable coating to exclude air and moisture.
copper alloys, and titanium. The bond strengths of the chro-
4. Racks and Anodes
mium varies with metallic substrate. Nevertheless, if the
procedures cited in the appropriate references are followed, the
4.1 Steel, cast iron, and stainless steel parts to be electro-
bond strength is such that grinding and honing can be con-
platedmayberackedatanyconvenientstageinthepreparatory
ducted without delamination of the coating.
process but preferably prior to the final cleaning and etching.
Aluminum, titanium, and certain nickel alloys may need to
3.2 Smoothness—The smoothness of the material surface to
have cleaning and etching operations done before racking due
be electroplated should be adequate to meet the requirements
to entrapment of cleaning and etching solutions in the plating
of the finished product. Chromium electrodeposits do not
rack which can result in adhesion failures due to seepage
exhibit leveling, and consequently the surface roughness of the
during chromium electroplating.
electrodeposit will always be greater than that of the substrate.
Any mechanical operations that can result in grinding checks 4.2 See Practice B507 for guidance on rack design, but note
or glazing of the metal are detrimental and should be elimi-
that while the general principles of good racking as used in
nated. The required surface smoothness may be obtained by other electroplating processes apply, the use of much higher
suitable chemical, mechanical, or electrochemical procedures.
current densities and the desirability of securing coatings of
Depending upon the thickness of the electrodeposit and the
uniform thickness and quality on desired areas require rack
smoothness required of the electrodeposit, grinding of the
constructiondesignsandmethodsthataremuchmoreexacting.
electrodeposit may be required.
The design of racks for chromium electroplating on the various
base metals previously mentioned for functional use should
3.3 Fatigue Considerations—Cracking that can occur in
provide for the following to the greatest possible extent.
chromium electrodeposits either as a function of the plating
4.2.1 There must be sufficient current-carrying capacity of
both cathode and anode circuits to all parts of the rack.
4.2.2 Theremustbepositiveelectricalcontacttothepartsto
AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS. beelectroplated,totheanodes,andtothetankcontactbusbars.
B177/B177M − 11 (2021)
4.2.3 There must be uniform current distribution on the also suitable. If parts have been shot-peened to develop a
parts to be electroplated. This often requires anodes of special compressively stressed surface, it is important to avoid remov-
shapes conforming to the shape of the part or area to be ing that surface by excessive grinding.
electroplated.
4.2.4 It may be necessary to use thieves, robbers, or guards,
6. Deoxidizing and Etching
which are auxiliary metallic conductors placed near points of
6.1 Prior to chromium electroplating, most metals need
abnormally high current density to attract the current away
special preparation in order to achieve maximum adhesion of
from such points; and shields, which are parts made of
the chromium to the substrate. Depending on the type and
nonconductive materials and placed to disperse the current in
nature of the metal and prior surface preparation steps, various
areas where it tends to concentrate unduly.
deoxidation and etching methods may be used to activate the
4.2.5 It is important to protect areas that are to remain free
substrate prior to chromium electroplating.
of any chromium electroplate by the use of masks made of
6.1.1 Aluminum—Chromium may be electroplated directly
rigid, nonconductive materials placed against the substrate, or
onto most cast and wrought aluminum materials used for
stop-offs, which are especially compounded nonconductive
engineering purposes. Guide B253 offers many useful methods
tapes, waxes, lacquers, or plastics for the protection of such
for preparing aluminum prior to chromium electroplating. The
substrates. Lead and aluminum tapes will provide a sharp line
removaloftheever-present,tenaciousoxidefilmonthesurface
of demarcation between coated and uncoated areas with a
ofaluminumiswhatmakeselectroplatingdifficult.Whenusing
minimum of buildup.
test methods in which a zinc immersion film is applied to the
4.2.6 Plugs (conducting and nonconducting) may be used in
aluminum surface for protection against oxide formation, the
holes not requiring electroplating to produce a sharp edge
article to be plated must enter the chromium-plating solution
without grooves around the periphery of the holes.
under live current.
4.2.7 It is very important to remember that improperly
6.1.2 Titanium—Like aluminum, titanium has an ever-
applied stop-off materials or poorly designed racks can entrap
present tenacious oxide film that must be removed prior to
acids that can cause corrosion of the basis material or contami-
plating. Practice B481 offers many ways to prepare titanium
nation of the solutions used in subsequent operations, or both.
prior to chromium electroplating.
4.2.8 Construction materials must be used that are suffi-
6.1.3 Nickel Alloys—Several different activation methods
ciently insoluble and noncontaminating to provide the desired
are available in Practice B558 for the preparation of different
rack life.
nickel alloys. The main difficulty with these materials when
4.2.9 Components must be placed in such positions that gas
chromium plating is polarization of the nickel alloy surface
from the parts, rack, thieves, masks, and anodes escapes freely
priortoplatingwhichresultsindeactivationofthematerialand
and does not become entrapped so as to prevent electroplating
skip plating.
on areas that should be electroplated.
6.1.4 Copper and Copper Alloys—Practice B281 offers
4.3 Anodes—Lead anodes containing 4 to 6 % antimony, 4 many suitable methods for preparing copper and copper alloys
to 7 % tin, or 1 % silver, or a combination thereof, are
prior to chromium electroplating. In general, only deoxidizing
satisfactory. Chemical lead is also satisfactory where hardness
of the copper or copper alloy surface is necessary for chro-
and rigidity are not important. However, it tends to form great
mium electroplating.
quantities of scale that may fall off on the work and cause
6.1.5 Stainless Steel—Practice B254 offers many suitable
pitting or roughness. Lead wire used for small anodes should
activating procedures for the preparation of stainless steel prior
contain 0.25 % antimony to obtain the best relationship be-
to chromium electroplating. Some stainless steels benefit from
tween rigidity and ductility in close tolerance areas. Lead-
a Woods nickel strike prior to chromium electroplating. Polar-
sheathedsteel,copper,orsilvermaybeusedwhenindicatedby
ized surfaces in high-nickel stainless steels can cause skip
requireme
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