ASTM B650-95(2002)
(Specification)Standard Specification for Electrodeposited Engineering Chromium Coatings on Ferrous Substrates
Standard Specification for Electrodeposited Engineering Chromium Coatings on Ferrous Substrates
SCOPE
1.1 This specification covers the requirements for electrodeposited chromium coatings applied to ferrous alloys for engineering applications.
1.2 Electrodeposited engineering chromium, which is sometimes called "functional" or "hard" chromium, is usually applied directly to the basis metal and is much thicker than decorative chromium. Engineering chromium is used for the following:
1.2.1 To increase wear and abrasion resistance,
1.2.2 To increase fretting resistance,
1.2.3 To reduce static and kinetic friction,
1.2.4 To reduce galling or seizing, or both, for various metal combinations,
1.2.5 To increase corrosion resistance, and
1.2.6 To build up undersize or worn parts.
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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Designation: B 650 – 95 (Reapproved 2002)
Standard Specification for
Electrodeposited Engineering Chromium Coatings on
Ferrous Substrates
This standard is issued under the fixed designation B 650; 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 Coating Thicknesses by Microscopical Examination of a
Cross Section
1.1 This specification covers the requirements for electrode-
B 499 Test Method for Measurement of Coating Thick-
posited chromium coatings applied to ferrous alloys for engi-
nessesbytheMagneticMethod:NonmagneticCoatingson
neering applications.
Magnetic Basis Metals
1.2 Electrodepositedengineeringchromium,whichissome-
B 504 Test Method for Measurement of Thickness of Me-
times called “functional” or “hard” chromium, is usually
tallic Coatings by the Coulometric Method
applied directly to the basis metal and is much thicker than
B 507 PracticeforDesignofArticlestoBeElectroplatedon
decorative chromium. Engineering chromium is used for the
Racks
following:
B 568 Test Method for Measurement of Coating Thickness
1.2.1 To increase wear and abrasion resistance,
by X-Ray Spectrometry
1.2.2 To increase fretting resistance,
B 571 Practice for QualitativeAdhesion Testing of Metallic
1.2.3 To reduce static and kinetic friction,
Coatings
1.2.4 To reduce galling or seizing, or both, for various metal
B 602 Test Method for Attribute Sampling of Metallic and
combinations,
Inorganic Coatings
1.2.5 To increase corrosion resistance, and
B 697 Guide for Selection of Sampling Plans for Inspection
1.2.6 To build up undersize or worn parts.
of Electrodeposited Metallic and Inorganic Coatings
1.3 This standard does not purport to address all of the
B 762 Test Method of Variables Sampling of Metallic and
safety concerns, if any, associated with its use. It is the
Inorganic Coatings
responsibility of the user of this standard to establish appro-
B 849 Specification for Pre-Treatments of Iron or Steel for
priate safety and health practices and determine the applica-
Reducing the Risk of Hydrogen Embrittlement
bility of regulatory limitations prior to use.
B 850 Guide for Post-Coating Treatments of Steel for Re-
2. Referenced Documents ducing Risk of Hydrogen Embrittlement
D 3951 Practice for Commercial Packaging
2.1 ASTM Standards:
E 8 TestMethodsforTensionTestingofMetallicMaterials
B 117 Practice for Operating Salt Spray (Fog) Apparatus
F 1459 Test Method for Determination of the Susceptibility
B 177 Guide for Engineering Chromium Electroplating
ofMetallicMaterialstoGaseousHydrogenEmbrittlement
B 183 Practice for Preparation of Low-Carbon Steel for
2.2 Other Standard:
Electroplating
MIL-S-13165 Shot Peening of Metal Parts
B 242 Guide for Preparation of High-Carbon Steel for
Electroplating
3. Terminology
B 320 Practice for Preparation of Iron Castings for Electro-
3.1 Definitions:
plating
3.1.1 significant surfaces—all surfaces upon which a de-
B 374 Terminology Relating to Electroplating
posit of controlled thickness is required.
B 487 Test Method for Measurement of Metal and Oxide
3.1.1.1 Discussion—When a controlled deposit is required
in holes, corners, recesses, and similar areas, special racking,
This specification is under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatingsand is the direct responsibility of Subcommittee
B08.08.01on Engineering Coatings. Annual Book of ASTM Standards, Vol 15.09.
Current edition approved Nov. 10, 1995. Published January 1996. Originally Annual Book of ASTM Standards, Vol 03.01.
e1 6
published as B 650 – 78. Last previous edition B 650 – 93 . Annual Book of ASTM Standards, Vol 15.03.
2 7
Annual Book of ASTM Standards, Vol. 03.02 AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
Annual Book of ASTM Standards, Vol 02.05. Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B 650
auxiliary anodes or shielding, or both, will be necessary. With unless other arrangements have been made between the pur-
the best practices there will be areas where a controlled deposit chaser and the electroplating facility.
is impossible.
3.2 Definitions used in this specification are in accordance 6. Coating Requirements
with Terminology B 374.
6.1 The appearance of the chromium coating on the signifi-
cant surfaces of the product shall be smooth and free of visual
4. Classification
defects such as blisters, pits, roughness, cracks, burned depos-
4.1 Electrodeposited chromium coatings in accordance with its, uncoated areas, or macrocracking of the deposit that is
visible without magnification.The boundaries of electroplating
this specification are classified by the thickness of the coating
as follows: that cover only a portion of the surface shall, after finishing as
indicated on the drawing, be free of beads, nodules, jagged
Class No. Chromium Thickness, µm Typical Application
edges, or other irregularities that will interfere with the
1 2.5 to 25 reduce friction; anti-galling, light
functioningoftheplatedpart.Imperfectionsandvariationsthat
wear resistance
arise from surface conditions of the basis metal (scratches,
2 >25 as specified buildup to dimension specified for
salvage or as required for severe
pores, roll marks, inclusions, etc.) and that persist in the finish
wear resistance
despite the observance of good metal finishing practices shall
4.2 Unless otherwise specified by suitably marked drawings not be cause for rejection.
or samples, only those surfaces that can be touched with a
NOTE 1—Applied finishes generally perform better in service when the
20-mm diameter ball shall be considered significant. In holes,
substrate over which they are applied is smooth and free of torn metal,
corners, recesses, and other areas where a controlled deposit
inclusions, pores, and other defects. It is recommended that the specifi-
cannot be obtained under normal electroplating conditions, the
cations covering the unfinished product provide limits for these defects.A
metal finisher can often remove defects through special treatments such as
thickness of the deposit may be that which results from control
grinding, polishing, abrasive blasting, chemical treatments, and elec-
on the significant surfaces.
tropolishing, which are not normal in the treatment steps preceding the
application of the finish and will add to the cost. When they are desired,
5. Ordering Information
they are the subject of a special agreement between the purchaser and the
seller.
5.1 The purchaser shall exercise the desired options of this
standard. Ordering documents shall specify the following
6.2 In cases where design for maximum fatigue life is a
information:
consideration the parts should be shot peened (see MIL-S-
5.1.1 Title,ASTM designation, and issue date of this speci-
13165C) or given an alternate mechanical treatment to com-
fication,
pressively stress the surface.
5.1.2 Alloy and metallurgical condition of the product to be
6.3 Stress Relief Treatment (See headnote at the beginning
chromium plated,
of this specification.):
5.1.3 Ultimate tensile strength of the material to be plated,
6.3.1 All steel parts having an ultimate tensile strength of
5.1.4 Heat treatment required for stress relief and whether it
1000 MPa (150 000 psi—approximately 32 HRC) or greater,
has been performed or is required,
that may contain residual stress caused by various fabrication
5.1.5 The significant surfaces if different from the 20-mm
operations such as machining, grinding, straightening, or cold
ball rule (see 3.1.1),
forming, will require one of the stress relief heat treatments
5.1.6 Thickness of the deposit or class (see 4.1),
prescribed in Specification B 849 prior to electroplating. In all
5.1.7 Control record requirements,
cases, the duration of heat treatment shall commence from the
5.1.8 Preproduction test specimens, if required,
time at which the whole of each part attains the specified
5.1.9 Sampling plan, if different from that specified in Test
temperature.
Method B 602 (see Section 8),
6.3.1.1 The treatment selected, of necessity, must be based
5.1.10 The number of test specimens for destructive testing
upon experience with the part or empirical test data.Therefore,
(see 7.1),
Class SR-0 treatment is provided for parts that the purchaser
5.1.11 Thickness, adhesion, porosity, and hydrogen em-
wishes to exempt from treatment. However, many, if not most,
brittlement tests required (see Section 6),
steels with a tensile strength in excess of 1000 MPa will
5.1.12 Whetherseparatetestspecimenswillbeused(see7.1
become embrittled when plated with chromium. The stress
and 7.5), relief and hydrogen embrittlement relief treatments are essen-
5.1.13 Where required, any special requirements for parts
tial for the safe performance of chromium plated items
that are subsequently ground to size, fabricated from those steels. Selection of Class SR-0 or ER-0
5.1.14 Where required, the base metal finish in terms of
requires thorough knowledge of the embrittlement susceptibil-
center line average (CLA) or arithmetic average (AA), and ityofthespecificsteelemployed.Whenthepurchaserspecifies
5.1.15 Where required, dimensional tolerances allowed for Class SR-0 or ER-0, the purchaser assumes sole responsibility
the specified coating thickness or class. for any embrittlement failure of the part. The relative suscep-
5.2 The manufacturer of the parts to be electroplated shall tibility of a steel can be determined by subjecting it to the Disk
provide the electroplating facility with test specimens (see Rupture Test of Test Method F 1459. When no stress relief
Section 7) to be electroplated for conformance tests as re- treatmentisspecifiedbythepurchaserthenClassSR-1shallbe
quested for preparation, control, inspection, and lot acceptance applied.
B 650
6.3.2 Parts having surface hardened areas that would suffer shallbecauseforrejection.Strippingandreplatingispermitted
an unacceptable reduction in hardness by treatment in accor- but parts having an ultimate tensile strength greater than 1000
dance with Specification B 849 shall be heat-treated at a lower MPa or a hardness greater than 32 HRC that are acid stripped
temperature but not less than 130°C for a minimum period of shall be rebaked (see 6.3) before plating. Baking after stripping
8 h.This treatment is applicable for parts made of steel with an is not necessary if the parts are stripped anodically in an
actual tensile strength below 1400 MPa. The purchaser may alkaline solution.
require that the heat-treatment temperature shall not reduce the 6.9 Supplemental Requirements—If parts are electroplated
surface hardness. Shorter times at higher temperatures may be and subsequently ground to size, the grinding shall be done
used, if the resulting loss of surface hardness is acceptable. with a proper coolant, never dry, and with a sufficiently light
6.3.3 If stress relief is given after shot peening or other cold cut to prevent cracking. Macrocracking, visually observed
working processes to introduce beneficial compressive without magnification after grinding, shall be cause for rejec-
stresses, the temperature shall not exceed 230°C. tion.
6.10 Packaging—Part(s) plated for the U.S. Government
6.4 Hydrogen Embrittlement Relief:
and Military, including subcontracts, shall be packaged in
6.4.1 Heat treatment appropriate for the tensile strength of
accordance with Practice D 3951.
the electroplated part (see Specification B 850) shall be per-
formed to reduce the risk of hydrogen embrittlement. In all
7. Test Methods
cases, the duration of the heat treatment shall commence from
7.1 Separate Specimens—When the coated articles are of
the time at which the whole part attains the specified tempera-
such a form as not to be readily adaptable to a test specified
ture. See 6.3.1.1 for important embrittlement relief information
herein, when destructive tests would unreasonably reduce the
regarding the selection of ER-0. When no embrittlement relief
number or pieces in small lots, when the pieces are too
treatmentisspecifiedbythepurchaserthenClassER-1shallbe
valuable to be destroyed, and when specified by the purchaser,
applied.
tests shall be made by the use of separate specimens plated
6.4.2 Begin the embrittlement relief heat-treatment as soon
concurrently with the articles represented. The separate speci-
aspracticalfollowingtheplatingprocessbutnolongerthan1.5
mens shall be of a basis metal equivalent to that of the articles
h.
represented. Equivalent basis metal includes chemical compo-
6.4.3 Parts or representative specimens shall be tested for
sition, grade, condition, and finish of surface prior to electro-
compliance in accordance with 7.5.
plating. The purchaser is responsible for providing these
6.5 Thickness—The thickness of the coating everywhere on
specimens (see section 5.3). These specimens shall be intro-
the significant surface(s) shall conform to the requirements of
duced into a lot before the cleaning operations preliminary to
the specified class as defined in Section 3 (see 7.2).
electroplating and shall not be separated therefrom until after
NOTE 2—The coating thickness requirements of this specification are a
completion of electroplating. Conditions affecting the electro-
minimumrequirement,thatis,thecoatingthicknessisrequiredtoequalor
plating of specimens, including the spacing and positioning in
exceed the specified thickness everywhere on the significant surfaces (see
respect to anodes and to other objects being electroplated, shall
4.1). Variation in the coating thickness from point to point on a coated
correspond as nearly as practicable to those affecting the
article is an inherent characteristic of electroplating processes. Therefore,
significant surfaces of the articles represented. Unless a need
the coating thickness must exceed the specified value at some point on the
can be demonstrated, separately prepared specimens shall not
significant surfaces to ensure that the thickness equals or exceeds the
specified value at all points. Hence, in most cases, the average coating
be used in place of production items for nondestructive tests
thickness on an article will be greater than the specified value; how much
and visual examination.
greater is largely determined by the shape of the article (see Practice
7.2 Thickness—Measure the thickness of the
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