ASTM B650-95(2013)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:B650 −95 (Reapproved 2013)
Standard Specification for
Electrodeposited Engineering Chromium Coatings on
Ferrous Substrates
This standard is issued under the fixed designation B650; 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 B320 Practice for Preparation of Iron Castings for Electro-
plating
1.1 This specification covers the requirements for electrode-
B374 Terminology Relating to Electroplating
posited chromium coatings applied to ferrous alloys for engi-
B487 Test Method for Measurement of Metal and Oxide
neering applications.
Coating Thickness by Microscopical Examination of
1.2 Electrodepositedengineeringchromium,whichissome-
Cross Section
times called “functional” or “hard” chromium, is usually
B499 Test Method for Measurement of Coating Thicknesses
applied directly to the basis metal and is much thicker than
by the Magnetic Method: Nonmagnetic Coatings on
decorative chromium. Engineering chromium is used for the
Magnetic Basis Metals
following:
B504 Test Method for Measurement of Thickness of Metal-
1.2.1 To increase wear and abrasion resistance,
lic Coatings by the Coulometric Method
1.2.2 To increase fretting resistance,
B507 Practice for Design of Articles to Be Electroplated on
1.2.3 To reduce static and kinetic friction,
Racks
1.2.4 Toreducegallingorseizing,orboth,forvariousmetal
B568 Test Method for Measurement of Coating Thickness
combinations,
by X-Ray Spectrometry
1.2.5 To increase corrosion resistance, and
B571 Practice for Qualitative Adhesion Testing of Metallic
1.2.6 To build up undersize or worn parts.
Coatings
1.3 This standard does not purport to address all of the B602 Test Method for Attribute 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- B697 Guide for Selection of Sampling Plans for Inspection
priate safety and health practices and determine the applica- of Electrodeposited Metallic and Inorganic Coatings
bility of regulatory limitations prior to use.
B762 Test Method of Variables Sampling of Metallic and
Inorganic Coatings
2. Referenced Documents
B849 Specification for Pre-Treatments of Iron or Steel for
2 Reducing Risk of Hydrogen Embrittlement
2.1 ASTM Standards:
B850 GuideforPost-CoatingTreatmentsofSteelforReduc-
B117 Practice for Operating Salt Spray (Fog) Apparatus
ing the Risk of Hydrogen Embrittlement
B177 Guide for Engineering Chromium Electroplating
D3951 Practice for Commercial Packaging
B183 Practice for Preparation of Low-Carbon Steel for
E8 Test Methods for Tension Testing of Metallic Materials
Electroplating
F1459 Test Method for Determination of the Susceptibility
B242 Guide for Preparation of High-Carbon Steel for Elec-
of Metallic Materials to Hydrogen Gas Embrittlement
troplating
(HGE)
2.2 Other Standard:
MIL-S-13165 Shot Peening of Metal Parts
This specification 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.
3. Terminology
Current edition approved Dec. 1, 2013. Published December 2013. Originally
3.1 Definitions:
approvedin1978.Lastpreviouseditionapprovedin2008asB650 – 95(2008).DOI:
10.1520/B0650-95R13.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
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B650−95 (2013)
3.1.1 significant surfaces—all surfaces upon which a de- 5.2 The manufacturer of the parts to be electroplated shall
posit of controlled thickness is required. provide the electroplating facility with test specimens (see
3.1.1.1 Discussion—When a controlled deposit is required Section 7) to be electroplated for conformance tests as re-
in holes, corners, recesses, and similar areas, special racking, quested for preparation, control, inspection, and lot acceptance
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.
6. Coating Requirements
3.2 Definitions used in this specification are in accordance
with Terminology B374.
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
deposits, uncoated areas, or macrocracking of the deposit that
4.1 Electrodeposited chromium coatings in accordance with
is visible without magnification.The boundaries of electroplat-
this specification are classified by the thickness of the coating
ing that cover only a portion of the surface shall, after finishing
as follows:
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
on the significant surfaces.
electropolishing,whicharenotnormalinthetreatmentstepsprecedingthe
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
13165C) or given an alternate mechanical treatment to com-
specification,
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 B849 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 B602 (see Section 8),
5.1.10 The number of test specimens for destructive testing 6.3.1.1 The treatment selected, of necessity, must be based
(see 7.1), upon experience with the part or empirical test data.Therefore,
5.1.11 Thickness, adhesion, porosity, and hydrogen em- Class SR-0 treatment is provided for parts that the purchaser
brittlement tests required (see Section 6), wishes to exempt from treatment. However, many, if not most,
5.1.12 Whetherseparatetestspecimenswillbeused(see7.1 steels with a tensile strength in excess of 1000 MPa will
and 7.5), become embrittled when plated with chromium. The stress
5.1.13 Where required, any special requirements for parts relief and hydrogen embrittlement relief treatments are essen-
that are subsequently ground to size, tial for the safe performance of chromium plated items
5.1.14 Where required, the base metal finish in terms of fabricated from those steels. Selection of Class SR-0 or ER-0
center line average (CLA) or arithmetic average (AA), and requires thorough knowledge of the embrittlement susceptibil-
5.1.15 Where required, dimensional tolerances allowed for ityofthespecificsteelemployed.Whenthepurchaserspecifies
the specified coating thickness or class. Class SR-0 or ER-0, the purchaser assumes sole responsibility
B650−95 (2013)
for any embrittlement failure of the part. The relative suscep- 6.7 The coating shall be sufficiently free of pores to pass the
tibility of a steel can be determined by subjecting it to the Disk porosity test specified (see 7.4).
Rupture Test of Test Method F1459. When no stress relief
6.8 Workmanship—Adding to (spotting in) or double
treatmentisspecifiedbythepurchaserthenClassSR-1shallbe
electroplating, unless evidence of a satisfactory bond is
applied.
established,shallbecauseforrejection.Strippingandreplating
6.3.2 Parts having surface hardened areas that would suffer
is permitted but parts having an ultimate tensile strength
an unacceptable reduction in hardness by treatment in accor-
greater than 1000 MPa or a hardness greater than 32 HRC that
dance with Specification B849 shall be heat-treated at a lower
are acid stripped shall be rebaked (see 6.3) before plating.
temperature but not less than 130°C for a minimum period of
Baking after stripping is not necessary if the parts are stripped
8 h.This treatment is applicable for parts made of steel with an
anodically in an alkaline solution.
actual tensile strength below 1400 MPa. The purchaser may
6.9 Supplemental Requirements—If parts are electroplated
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 D3951.
the electroplated part (see Specification B850) 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
6.4.3 Parts or representative specimens shall be tested for
composition, grade, condition, and finish of surface prior to
compliance in accordance with 7.5.
electroplating.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
minimumrequirement,thatis,thecoatingthicknessisrequiredtoequalor
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
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