ASTM B650-95
(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.
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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Designation: B 650 – 95
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 B 499 Test Method for Measurement of Coating Thickness
by the Magnetic Method: Nonmagnetic Coatings on Mag-
1.1 This specification covers the requirements for electrode-
netic Basis Metals
posited chromium coatings applied to ferrous alloys for engi-
B 504 Test Method for Measurement of Thickness of Me-
neering applications.
tallic Coatings by the Coulometric Method
1.2 Electrodeposited engineering chromium, which is some-
B 507 Practice for Design of Articles to Be Electroplated on
times called “functional” or “hard” chromium, is usually
Racks
applied directly to the basis metal and is much thicker than
B 568 Test Method for Measurement of Coating Thickness
decorative chromium. Engineering chromium is used for the
by X-Ray Spectrometry
following:
B 571 Test Methods for Adhesion of Metallic Coatings
1.2.1 To increase wear and abrasion resistance,
B 602 Test Method for Attribute Sampling of Metallic and
1.2.2 To increase fretting resistance,
Inorganic Coatings
1.2.3 To reduce static and kinetic friction,
B 697 Guide for Selection of Sampling Plans for Inspection
1.2.4 To reduce galling or seizing, or both, for various metal
of Electrodeposited Metallic and Inorganic Coatings
combinations,
B 762 Method of Variables Sampling of Metallic and Inor-
1.2.5 To increase corrosion resistance, and
ganic Coatings
1.2.6 To build up undersize or worn parts.
B 849 Specification for Pre-Treatments of Iron or Steel for
1.3 This standard does not purport to address all of the
Reducing the Risk of Hydrogen Embrittlement
safety concerns, if any, associated with its use. It is the
B 850 Specification for Post-Coating Treatments of Iron or
responsibility of the user of this standard to establish appro-
Steel for Reducing the Risk of Hydrogen Embrittlement
priate safety and health practices and determine the applica-
D 3951 Practice for Commercial Packaging
bility of regulatory limitations prior to use.
E 8 Test Methods for Tension Testing of Metallic Materials
2. Referenced Documents F 1459 Test Method for Determination of the Susceptibility
of Metallic Materials to Gaseous Hydrogen Embrittlement
2.1 ASTM Standards:
2.2 Other Standard:
B 117 Practice for Operating Salt Spray (Fog) Apparatus
MIL-S-13165 Shot Peening of Metal Parts
B 177 Practice for Chromium Electroplating on Steel for
Engineering Use
3. Terminology
B 183 Practice for Preparation of Low-Carbon Steel for
2 3.1 Definitions:
Electroplating
3.1.1 significant surfaces—all surfaces upon which a de-
B 242 Practice for Preparation of High-Carbon Steel for
2 posit of controlled thickness is required.
Electroplating
3.1.1.1 Discussion—When a controlled deposit is required
B 320 Practice for Preparation of Iron Castings for Electro-
2 in holes, corners, recesses, and similar areas, special racking,
plating
auxiliary anodes or shielding, or both, will be necessary. With
B 374 Terminology Relating to Electroplating
the best practices there will be areas where a controlled deposit
B 487 Test Method for Measurement of Metal and Oxide
is impossible.
Coating Thickness by Microscopical Examination of a
2 3.2 Definitions used in this specification are in accordance
Cross Section
with Terminology B 374.
This specification is under the jurisdiction of ASTM Committee B-8 on
Metallic and Inorganic Coatingsand is the direct responsibility of Subcommittee Annual Book of ASTM Standards, Vol 15.09.
B08.08.01on Engineering Coatings. Annual Book of ASTM Standards, Vol 03.01.
Current edition approved Nov. 10, 1995. Published January 1996. Originally Annual Book of ASTM Standards, Vol 15.03.
e1 6
published as B 650 – 78. Last previous edition B 650 – 93 . Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700
Annual Book of ASTM Standards, Vol 02.05. Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
B 650
4. Classification defects such as blisters, pits, roughness, cracks, burned depos-
its, uncoated areas, or macrocracking of the deposit that is
4.1 Electrodeposited chromium coatings in accordance with
visible without magnification. The boundaries of electroplating
this specification are classified by the thickness of the coating
that cover only a portion of the surface shall, after finishing as
as follows:
indicated on the drawing, be free of beads, nodules, jagged
Chromium Thickness, μm
edges, or other irregularities that will interfere with the
Class No. Typical Application
functioning of the plated part. Imperfections and variations that
1 2.5 to 25 reduce friction; anti-galling, light
arise from surface conditions of the basis metal (scratches,
wear resistance
pores, roll marks, inclusions, etc.) and that persist in the finish
2 >25 as specified buildup to dimension specified for
salvage or as required for severe
despite the observance of good metal finishing practices shall
wear resistance
not be cause for rejection.
4.2 Unless otherwise specified by suitably marked drawings
NOTE 1—Applied finishes generally perform better in service when the
or samples, only those surfaces that can be touched with a
substrate over which they are applied is smooth and free of torn metal,
20-mm diameter ball shall be considered significant. In holes,
inclusions, pores, and other defects. It is recommended that the specifi-
corners, recesses, and other areas where a controlled deposit
cations covering the unfinished product provide limits for these defects. A
cannot be obtained under normal electroplating conditions, the metal finisher can often remove defects through special treatments such as
grinding, polishing, abrasive blasting, chemical treatments, and elec-
thickness of the deposit may be that which results from control
tropolishing, which are not normal in the treatment steps preceding the
on the significant surfaces.
application of the finish and will add to the cost. When they are desired,
they are the subject of a special agreement between the purchaser and the
5. Ordering Information
seller.
5.1 The purchaser shall exercise the desired options of this
6.2 In cases where design for maximum fatigue life is a
standard. Ordering documents shall specify the following
consideration the parts should be shot peened (see MIL-S-
information:
13165C) or given an alternate mechanical treatment to com-
5.1.1 Title, ASTM designation, and issue date of this speci-
pressively stress the surface.
fication,
6.3 Stress Relief Treatment (See headnote at the beginning
5.1.2 Alloy and metallurgical condition of the product to be
of this specification.):
chromium plated,
6.3.1 All steel parts having an ultimate tensile strength of
5.1.3 Ultimate tensile strength of the material to be plated,
1000 MPa (150 000 psi—approximately 32 HRC) or greater,
5.1.4 Heat treatment required for stress relief and whether it
that may contain residual stress caused by various fabrication
has been performed or is required,
operations such as machining, grinding, straightening, or cold
5.1.5 The significant surfaces if different from the 20-mm
forming, will require one of the stress relief heat treatments
ball rule (see 3.1.1),
prescribed in Specification B 849 prior to electroplating. In all
5.1.6 Thickness of the deposit or class (see 4.1),
cases, the duration of heat treatment shall commence from the
5.1.7 Control record requirements,
time at which the whole of each part attains the specified
5.1.8 Preproduction test specimens, if required,
temperature.
5.1.9 Sampling plan, if different from that specified in Test
6.3.1.1 The treatment selected, of necessity, must be based
Method B 602 (see Section 8),
upon experience with the part or empirical test data. Therefore,
5.1.10 The number of test specimens for destructive testing
Class SR-0 treatment is provided for parts that the purchaser
(see 7.1),
wishes to exempt from treatment. However, many, if not most,
5.1.11 Thickness, adhesion, porosity, and hydrogen em-
steels with a tensile strength in excess of 1000 MPa will
brittlement tests required (see Section 6),
become embrittled when plated with chromium. The stress
5.1.12 Whether separate test specimens will be used (see 7.1
and 7.5), relief and hydrogen embrittlement relief treatments are essen-
tial for the safe performance of chromium plated items
5.1.13 Where required, any special requirements for parts
that are subsequently ground to size, fabricated from those steels. Selection of Class SR-0 or ER-0
requires thorough knowledge of the embrittlement susceptibil-
5.1.14 Where required, the base metal finish in terms of
center line average (CLA) or arithmetic average (AA), and ity of the specific steel employed. When the purchaser specifies
Class SR-0 or ER-0, the purchaser assumes sole responsibility
5.1.15 Where required, dimensional tolerances allowed for
the specified coating thickness or class. for any embrittlement failure of the part. The relative suscep-
tibility of a steel can be determined by subjecting it to the Disk
5.2 The manufacturer of the parts to be electroplated shall
Rupture Test of Test Method F 1459. When no stress relief
provide the electroplating facility with test specimens (see
treatment is specified by the purchaser then Class SR-1 shall be
Section 7) to be electroplated for conformance tests as re-
applied.
quested for preparation, control, inspection, and lot acceptance
6.3.2 Parts having surface hardened areas that would suffer
unless other arrangements have been made between the pur-
chaser and the electroplating facility. an unacceptable reduction in hardness by treatment in accor-
dance with Specification B 849 shall be heat-treated at a lower
6. Coating Requirements
temperature but not less than 130°C for a minimum period of
6.1 The appearance of the chromium coating on the signifi- 8 h. This treatment is applicable for parts made of steel with an
cant surfaces of the product shall be smooth and free of visual actual tensile strength below 1400 MPa. The purchaser may
B 650
require that the heat-treatment temperature shall not reduce the and subsequently ground to size, the grinding shall be done
surface hardness. Shorter times at higher temperatures may be with a proper coolant, never dry, and with a sufficiently light
used, if the resulting loss of surface hardness is acceptable. cut to prevent cracking. Macrocracking, visually observed
6.3.3 If stress relief is given after shot peening or other cold without magnification after grinding, shall be cause for rejec-
working processes to introduce beneficial compressive tion.
stresses, the temperature shall not exceed 230°C. 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-
7. Test Methods
formed to reduce the risk of hydrogen embrittlement. In all
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
treatment is specified by the purchaser then Class ER-1 shall be
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-
as practical following the plating process but no longer than 1.5
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
completion of electroplating. Conditions affecting the electro-
NOTE 2—The coating thickness requirements of this specification are a
plating of specimens, including the spacing and positioning in
minimum requirement, that is, the coating thickness is required to equal or
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
be used in place of production items for nondestructive tests
specified value at all points. Hence, in most cases, the average coating
and visual examination.
thickness on an article will be greater than the specified value; how much
7.2 Thickness—Measure the thickness of the chromium by
greater is largely determined by the shape of the article (see Practice
B 507) and the characteristics of the electroplating process. In addition,
one of the following methods; other methods may be used if it
the average coating thickness on articles will vary from article to article
can be demonstrated that the uncertainty of the method is less
within a production lot. Therefore, if all of the
...
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