ASTM B456-17(2022)

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:B456 −17 (Reapproved 2022)
Standard Specification for
Electrodeposited Coatings of Copper Plus Nickel Plus
Chromium and Nickel Plus Chromium
This standard is issued under the fixed designation B456; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber 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
2.1 ASTM Standards:
1.1 This specification covers requirements for several types
B183Practice for Preparation of Low-Carbon Steel for
and grades of electrodeposited copper plus nickel plus chro-
Electroplating
mium or nickel plus chromium coatings on steel, nickel plus
B242Guide for Preparation of High-Carbon Steel for Elec-
chromium coatings on copper and copper alloys, nickel plus
troplating
chromium coatings on Type 300 and 400 series stainless steel
B252Guide for Preparation of Zinc Alloy Die Castings for
and copper plus nickel plus chromium coatings on aluminum
Electroplating and Conversion Coatings
and its alloys and zinc alloys for applications where both
B253Guide for Preparation of Aluminum Alloys for Elec-
appearance and protection of the basis metal against corrosion
troplating
are important. Five grades of coatings are provided to corre-
B254Practice for Preparation of and Electroplating on
spondwiththeserviceconditionsunderwhicheachisexpected
Stainless Steel
to provide satisfactory performance: namely, extended very
B281Practice for Preparation of Copper and Copper-Base
severe, very severe, severe, moderate, and mild. Definitions
Alloys for Electroplating and Conversion Coatings
and typical examples of these service conditions are provided
B320Practice for Preparation of Iron Castings for Electro-
in Appendix X1.
plating
B368Test Method for Copper-AcceleratedAceticAcid-Salt
1.2 This specification does not cover the requirements for
Spray (Fog) Testing (CASS Test)
the plating on plastics, see Specification B604.
B380Test Method for Corrosion Testing of Decorative
1.3 The following hazards caveat pertains only to the test Electrodeposited Coatings by the Corrodkote Procedure
B487Test Method for Measurement of Metal and Oxide
methods portions, Appendix X2, Appendix X3, Appendix X4,
Coating Thickness by Microscopical Examination of
and Appendix X5 of this specification: This standard does not
Cross Section
purport to address all of safety concerns, if any, associated
B489Practice for Bend Test for Ductility of Electrodepos-
with its use. It is the responsibility of the user of this standard
ited and Autocatalytically Deposited Metal Coatings on
to establish appropriate safety, health, and environmental
Metals
practices and determine the applicability of regulatory limita-
B490Practice for Micrometer Bend Test for Ductility of
tions prior to use.
Electrodeposits
1.4 This international standard was developed in accor-
B499Test Method for Measurement of CoatingThicknesses
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-
B504Test 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.
B530Test Method for Measurement of CoatingThicknesses
by the Magnetic Method: Electrodeposited Nickel Coat-
ings on Magnetic and Nonmagnetic Substrates
This specification is under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.05 on Decorative Coatings. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2022. Published October 2022. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1967. Last previous edition approved in 2017 as B456–17. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/B0456-17R22. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B456−17 (2022)
B537Practice for Rating of Electroplated Panels Subjected 4.2.1 Theserviceconditionnumberindicatestheseverityof
to Atmospheric Exposure exposure for which the grade of coating is intended:
B568Test Method for Measurement of Coating Thickness SC 5 extended severe service
by X-Ray Spectrometry SC 4 very severe service,
B571Practice for Qualitative Adhesion Testing of Metallic SC 3 severe service,
Coatings SC 2 moderate service, and
B602Guide for Attribute Sampling of Metallic and Inor- SC 1 mild service.
ganic Coatings 4.2.2 Typical service conditions for which the various
B604Specification for Decorative Electroplated Coatings of service condition numbers are appropriate are given in Appen-
Copper Plus Nickel Plus Chromium on Plastics dix X1.
B659Guide for Measuring Thickness of Metallic and Inor-
4.3 Coating Classification Number—The coating classifica-
ganic Coatings
tion number comprises:
B697Guide for Selection of Sampling Plans for Inspection
4.3.1 The chemical symbol for the basis metal (or for the
of Electrodeposited Metallic and Inorganic Coatings
principalmetalifanalloy)followedbyaslashmark,exceptin
B762GuideofVariablesSamplingofMetallicandInorganic
the case of stainless steel. In this case, the designation shall be
Coatings
SS followed by the designated AISI number followed by a
B764Test Method for Simultaneous Thickness and Elec-
slash, that is, SS463/,
trode Potential Determination of Individual Layers in
4.3.2 The chemical symbol for copper (Cu) (if copper is
Multilayer Nickel Deposit (STEP Test)
used),
B995Test Method for Chloride Resistance Test for Chro-
4.3.3 A number indicating the minimum thickness of the
mium Electroplated Parts (Russian Mud Test)
copper coating in micrometers (if copper is used),
D1193Specification for Reagent Water
4.3.4 A lower-case letter designating the type of copper
D3951Practice for Commercial Packaging
deposit (if copper is used) (see 4.4 and 6.2.3),
E50Practices for Apparatus, Reagents, and Safety Consid-
4.3.5 The chemical symbol for nickel (Ni),
erations for Chemical Analysis of Metals, Ores, and
4.3.6 A number indicating the minimum thickness of the
Related Materials
nickel coating, in micrometers,
G85Practice for Modified Salt Spray (Fog) Testing
4.3.7 A lower-case letter designating the type of nickel
2.2 ISO Standards:
deposit (see 4.4 and 6.2.4),
ISO 1456Metallic coatings—Electrodeposited coatings of
4.3.8 The chemical symbol for chromium (Cr), and
nickel plus chromium and of copper plus nickel plus
4.3.9 A letter (or letters) designating the type of chromium
chromium
depositanditsminimumthicknessinmicrometers(see4.4and
6.2.5).
3. Terminology
4.4 Symbols for Expressing Classification—The following
3.1 Definitions:
lower-case letters shall be used in coating classification num-
3.1.1 significant surfaces—those surfaces normally visible
bers to describe the types of coatings:
(directlyorbyreflection)thatareessentialtotheappearanceor
a —ductile copper deposited from acid-type baths
serviceabilityofthearticle,orboth,whenassembledinnormal
b —single-layer nickel deposited in the fully-bright condition
position; or that can be the source of corrosion products that
d —double- or triple-layer nickel coatings
r —regular (that is, conventional) chromium
deface visible surfaces on the assembled article. When
mc —microcracked chromium
necessary, the significant surfaces shall be specified by the
mp —microporous chromium
purchaser and shall be indicated on the drawings of the parts,
4.5 Example of Complete Classification Numbers—A coat-
or by the provision of suitably marked samples.
ing on steel comprising 15 µm minimum (ductile acid) copper
3.1.2 p-points—specific points of measurement that are
plus 25 µm minimum (duplex) nickel plus 0.25µ m minimum
encouraged to be determined and agreed upon with the
(micro-cracked) chromium has the classification number: Fe/
customer early in the contract review process. These are used
Cu15aNi25d Cr mc (see 4.3 and 6.2 for explanation of
for measurement of critical characteristics that vary with
symbols).
current density such as thickness, STEP, active sites, etc. and
may be designated at multiple locations per part.
5. Ordering Information
5.1 When ordering articles to be electroplated in confor-
4. Classification
mance with this standard, the purchaser shall state the follow-
4.1 Five grades of coatings designated by service condition
ing:
numbersandseveraltypesofcoatingsdefinedbyclassification
5.1.1 The ASTM designation number of this standard.
numbers are covered by this specification.
5.1.2 Eithertheclassificationnumberofthespecificcoating
4.2 Service Condition Number:
required (see 4.3) or the substrate material and the service
condition number denoting the severity of the conditions it is
requiredtowithstand(see4.2).Iftheserviceconditionnumber
Available from International Organization for Standardization (ISO), 1, ch. de
isquotedandnottheclassificationnumber,themanufactureris
la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://
www.iso.ch. free to supply any of the types of coatings designated by the
B456−17 (2022)
TABLE 2 Copper Plus Nickel Plus Chromium Coatings on Steel
classification numbers corresponding to the specified service
condition number, as given in Table 1, Table 2, Table 3, Table Service Condition Classification No. Nickel Thickness,
No. µm
4,or Table 5. On request, the manufacturer shall inform the
SC 5 Fe/Cu15a Ni30d Cr mc 30
purchaser of the classification number of the coating applied.
Fe/Cu15a Ni30d Cr mp 30
5.1.3 The appearance required, for example, bright, dull, or
SC 4 Fe/Cu15a Ni25d Cr mc 25
satin. Alternatively, samples showing the required finish or Fe/Cu15a Ni25d Cr mp 25
SC 3 Fe/Cu12a Ni20d Cr mc 20
range of finish shall be supplied or approved by the purchaser.
Fe/Cu12a Ni20d Cr mp 20
5.1.4 The significant surfaces, to be indicated on drawings
of the parts, or by the provision of suitably marked specimens
(see 3.1).
TABLE 3 Copper Plus Nickel Plus Chromium Coatings on Zinc
5.1.5 The positions on significant surfaces for rack or
Alloy
contact marks, where such marks are unavoidable (see 6.1.1).
Service Condition
Classification No. Nickel Thickness, µm
5.1.6 The extent to which defects shall be tolerated on No.
SC 5 Zn/Cu5 Ni35d Cr mc 35
nonsignificant surfaces.
Zn/Cu5 Ni35d Cr mp 35
5.1.7 The elongation of copper if other than the standard
SC 4 Zn/Cu5 Ni30d Cr mc 30
value (see 6.4).
Zn/Cu5 Ni30d Cr mp 30
SC 3 Zn/Cu5 Ni20d Cr mc 20
5.1.8 The ductility of the nickel if other than the standard
Zn/Cu5 Ni20d Cr mp 20
value (see 6.5).
SC 2 Zn/Cu5 Ni20b Cr r 20
5.1.9 The extent of tolerable surface deterioration after
Zn/Cu5 Ni15b Cr mc 15
corrosion testing (see 6.8.3). Zn/Cu5 Ni15b Cr mp 15
SC 1 Zn/Cu5 Ni10b Cr r 10
5.1.10 Sampling methods and acceptance levels (see Sec-
tion 7).
5.1.11 The minimum and maximum values of the electrode
TABLE 4 Nickel Plus Chromium Coatings on Copper or Copper
potential differences between individual nickel layers as mea-
Alloy
sured in accordance with Test Method B764 within the limits
Service Condition
Classification No. Nickel Thickness, µm
given in 6.9.
No.
5.1.12 Adhesion Test—The adhesion test to be used (see
SC 4 Cu/Ni25d Cr mc 25
Cu/Ni25d Cr mp 25
6.3).
SC 3 Cu/Ni20d Cr mc 20
Cu/Ni20d Cr mp 20
6. Product Requirements
Cu/Ni30b Cr r 30
Cu/Ni25b Cr mc 25
6.1 Visual Defects:
Cu/Ni25b Cr mp 25
6.1.1 The significant surfaces of the electroplated article
SC 2 Cu/Ni15b Cr r 15
shall be free of clearly visible plating defects, such as blisters,
Cu/Ni10b Cr mc 10
Cu/Ni10b Cr mp 10
pits, roughness, cracks, and uncoated areas and shall not be
SC 1 Cu/Ni5b Cr r 5
stained or discolored. On articles where a visible contact mark
is unavoidable, its position shall be agreed upon by the
purchaserandtheplater.Theelectroplatedarticleshallbeclean
6.1.2 Defects in the surface of the basis metal, such as
and free of damage.
scratches, porosity, nonconducting inclusions, roll and die
marks, cold shuts, weld imperfections, and cracks, may ad-
TABLE 1 Nickel Plus Chromium Coatings on Steel
versely affect the appearance and the performance of coatings
NOTE 1—When permitted by the purchaser, copper may be used as an
appliedtheretodespitetheobservanceofthebestelectroplating
undercoat for nickel but is not substitutable for any part of the nickel
practices.Accordingly, the plater’s responsibilityfor defects in
thicknessspecified.Iftheuseofcopperispermitted, Table2maybeused
the coating resulting from such conditions shall be waived.
to obtain the same service conditions.
NOTE1—Tominimizeproblemsofthistype,thespecificationscovering
NOTE2—Satinnickelmayreplaceorbedepositedoverthebrightnickel
the basis material or the item to be electroplated should contain appro-
layer per supplier recommendations.
priate limitations on such basis metal conditions. Furthermore, areas such
NOTE3—Substrateconditioncanhaveasignificantimpactoncorrosion
as welds may be excluded from certain performance criteria based upon
performance. mutual agreement of purchaser and supplier.
Service Condition Classification No. Nickel Thickness,
6.2 Process and Coating Requirements:
No. µm
6.2.1 Proper preparatory procedures and thorough cleaning
SC 5 Fe/Ni35d Cr mc 35
ofthebasismetalsurfaceareessentialforsatisfactoryadhesion
Fe/Ni35d Cr mp 35
SC 4 Fe/Ni30d Cr mc 30 and corrosion performance of the coating. Accordingly, the
Fe/Ni30d Cr mp 30
applicable practices for the preparation of various basis metals
SC 3 Fe/Ni25d Cr mc 25
for electroplating shall be followed. Practices B183, B242,
Fe/Ni25d Cr mp 25
SC 2 Fe/Ni20b Cr r 20 B252, B281, and B320 are examples of practices that may be
Fe/Ni15b Cr mc 15
used for the preparation of basis metals.
Fe/Ni15b Cr mp 15
6.2.2 Following the preparatory operations, the parts (ar-
SC 1 Fe/Ni10b Cr r 10
ticles) to be electroplated are introduced in such plating baths
B456−17 (2022)
A
TABLE 5 Nickel Plus Chromium on Stainless Steels, AISI
haveaminimumductilityof11%.Iftherearethreelayers,the
B
Designated Type 300 and 400 Series, and Copper Plus Nickel
intermediate layer shall contain not less than 0.15 mass%
Plus Chromium on Aluminum and Its Alloys
sulfur. These requirements for multilayer nickel coatings are
NOTE 1—Before nickel-chromium plating, the stainless steel surface
summarized in Table 6.
and the aluminum substrate shall be prepared by a pretreatment from
C D
Practice B254, Guide B253, or equivalent, which is agreed upon
NOTE 2—The percentages listed in Table 6 are intended to be a percent
between the supplier and the user.
of the minimum thickness required for a particular service condition.
Service Condition Nickel Thickness,
Therefore,theoverallratioofthenickellayersmaynotbeconsistentwith
Classification No.
No. µm
these values, but the minimum amount of nickel for each layer will be
E
SC 4 SS-3XX /Ni20b/Cr mp 20
present.Asanexample,adoublelayerapplicationrequiring35µmoftotal
E
SC 4 SS-4xx /Ni25b/Cr mp 25
nickelshouldhaveaminimumof21µm(60%)ofsemi-brightand14µm
SC 5 Al/Cu15a/Ni40d/Cr mp 40
(40%) of bright. Additional bright nickel may be added beyond the
A
Data in Table 5 were obtained using only microporous chromium systems. No minimumamountforcosmeticpurposes,whichwillalterthefinalratioof
data were available for the use of standard or microcracked systems. the two nickel layers but will still meet the minimum thickness require-
B
The stainless steel alloy numbers used in this specification are based on the AISI
ments.
system. They may not be interchangeable with other numbering systems such as
NOTE 3—The sulfur contents are specified in order to indicate which
the United Numbering System (UNS) or foreign designations.
type of nickel electroplating solution must be used. Although at present,
C
Preplate for stainless steel substrates.
no simple method is available for determining the sulfur content of a
D
Preplate for aluminum substrates.
nickel deposit on a coated article, chemical determinations are possible
E
Insert AISI number for specific 300 or 400 alloy.
using specially prepared test specimens (see Appendix X3). The correct
sulfur content has a significant effect on the corrosion performance of the
nickel deposits.
as required to produce the types of deposits described by the
NOTE 4—It will usually be possible to identify the type of nickel by
specific coating classification numbers or one of the coating microscopicalexaminationofthepolishedandetchedsectionofanarticle
prepared in accordance with Test Method B487. The thickness of the
classificationnumberslistedinTable1,Table2,Table3,Table
individual nickel layers in double-layer and triple-layer coatings, as well
4,or Table 5 appropriate for the specified service condition
as the electrochemical relationships between the individual layers, can
number.
also be measured by the STEP Test, in accordance with Test Method
6.2.3 Type of Copper and Deposit Thickness:
B764.
6.2.3.1 Type of Copper—The type of copper is designated
6.2.4.2 Thickness of Nickel Deposit—The number follow-
by the following symbols that are placed after the thickness
ing the chemical symbol Ni indicates, in micrometers, the
value:
minimumthicknessofthenickelelectrodepositatpointsonthe
a for ductile copper deposited from acid-type baths contain-
significant surface (see 3.1 and Note 5).
ing additives that promote leveling by the copper deposit and
6.2.5 Type of Chromium and Deposit Thickness:
that have an elongation not less than 8%.
6.2.5.1 Type of Chromium—The type of chromium deposit
No symbol is placed after the thickness value if a minimum
is designated by the following symbols placed after the
elongation is not required or if a deposit from a non-leveling
chemical symbol Cr:
bath is permitted.
r for “regular” (that is, conventional) chromium.
6.2.3.2 Thickness of Copper Deposits—The number follow-
mc for microcracked chromium, having more than 30
ing the chemical symbol for copper (Cu) indicates in microm-
cracks/mm in any direction (Appendix X4) over the whole of
eters the minimum thickness of the copper deposit at points on
the significant surface. The cracks shall be invisible to the
significant surfaces (see 3.1).
unaided eye (see 6.11).
6.2.4 Type of Nickel and Deposit Thickness:
mp for microporous chromium containing a minimum of
6.2.4.1 Type of Nickel—The type of nickel is designated by 2 2
10000 pores⁄10 by 10 mm (10000⁄cm ) using the Dubper-
the following symbols, which are placed after the thickness
nell method (Appendix X4), or a minimum of 2000 pores/10
value: 2 2
by 10 mm (2000 pores/cm ) using the active site method
b for nickel deposited in the fully bright condition.
(AppendixX5).Theporesshallbeinvisibletotheunaidedeye
d for a double-layer or triple-layer nickel coating.
(see 6.11).
The bottom layer of this coating system shall contain less
6.2.5.2 A specially formulated noble nickel in between the
than0.005mass%sulfur(Note3),andaminimumductilityof
bright nickel and the chromium deposits (see 6.9.4) may be
67% (see Practice B490). The top layer of this system shall
used to induce micropores or microcracks in the chromium
containmorethan0.04mass%sulfur(Note3andNote4),and
deposits.Thethicknessofthislayerisrecommendedtobe2to
4 µm minimum thickness. Controlled particle impingement of
TABLE 6 Summary of the Requirements for Double- and Triple-
the plated standard chromium deposit may also be used to
Layer Nickel Coatings
induce microporous chromium. Trivalent chromium deposits,
as plated, may be microporous, microcracked, or both.
Type of Sulfur Double Triple
Ductility
6.2.5.3 Thickness of Chromium Deposit—The minimum
Nickel Layer Content Layer Layer
thickness of the chromium deposit shall be 0.2 µm on signifi-
Bottom 67 % <0.005 mass % 60 to 80 % 50 to 70 %
cant surfaces (see 3.1), except that for service condition SC 1
Middle (high-sulfur) . >0.15 mass % . #10 %
Top (bright) 11 % >0.04 mass % 20 to 40 % (see $20 %
A
Note 2 )
A A A
Test Method See B490 See Note 3 See Note 4 See Note 4 4
Harbulak, E. P., “Simultaneous Thickness and Electrochemical Potential
A
Determination of Individual Layers in Multilayer Nickel Deposits,” Plating and
For Note 3 and Note 4, see Section 6.
Surface Finishing, Vol 67, No. 49, February 1980.
B456−17 (2022)
(see4.2.1)theminimumthicknessmaybereducedto0.13µm. total thickness of the nickel, and the thickness of the copper.
The thickness of chromium is designated by the same symbol The STEP test, Test Method B764, which is similar to the
as the type instead of by numerals as in the case of copper and coulometric method, may be used to closely estimate the
nickel. thicknesses of individual layers of nickel in a multilayer
coating.
NOTE5—Electroplatedchromiumdepositsconsistmainlyofchromium
6.7.3.2 ThemicroscopicalmethoddescribedinTestMethod
metalwithchromiumoxidesandothercompounds.Hexavalentchromium
B487 may be used to measure the thickness of each nickel
ions would only be present if the surface of the part is not thoroughly
rinsed. Rinsing is essential to meet regulations banning the presence of
layer and of the copper layer. In cases where thickness
hexavalent chromium ions on the part.
TABLE 7 Corrosion Tests Appropriate for Each Service Condition Number
Corrosion Test and Duration h
Service Condition
Basis Metals
CASS Method Acetic-salt Method
No.
Corrodkote Method B380
B368 G85
Steel, zinc alloy, SC 5 66 . .
or copper and SC 4 22 Two 16-h cycles 144
copper alloy, SC 3 16 16 96
stainless steel and SC 2 8 4 24
aluminum alloys SC 1 . . 8
6.2.5.4 When plating chromium over a nickel strike con- measurements conflict, microscopical will be the prevailing
taining micro-particles used to induce microporosity in the method.
subsequentchromiumdeposit,excesschromiumthicknesswill
6.7.3.3 The X-ray method described in Test Method B568
bridge the nonconductive particles within the nickel layer. A
may be used to measure thickness of the chromium, thickness
maximum of 0.5 µm is recommended.
ofasinglelayernickelaswellasthethicknessofcopper.Inthe
case of duplex/triple nickel coatings, the X-ray method will
6.3 Adhesion—The coating shall be sufficiently adherent to
give a total nickel thickness reading based on the average
the basis metal, and the separate layers of multilayer coatings
density of the individual nickel coatings.
shall be sufficiently adherent to each other, to pass the
6.7.3.4 Other methods may be used if it can be demon-
appropriatetestsdetailedinTestMethodsB571.Theparticular
strated that the uncertainty of the measurement is less than
test or tests to be used shall be specified by the purchaser.
10%, or less than that of any applicable method mentioned in
6.4 Elongation—Theelongationofcoppershallbesuchthat
6.7.3. Other methods such as B499 and B530, as outlined in
it will not be less than stated in 6.2.3.1 when tested by the
Guide B659, may be used if agreed upon between the pur-
method given in Appendix X2. Greater elongation may be
chaser and manufacturer.
requested but shall be subject to agreement between the
6.8 Corrosion Testing:
purchaser and the manufacturer.
6.8.1 Coated articles shall be subjected to the corrosion test
6.5 Ductility—The ductility of the composite nickel deposit
foraperiodoftimethatisappropriatefortheparticularservice
on a finished part is considered acceptable when foils plated
condition number (or for the service condition number corre-
outoftheindividualnickelprocessesmeetorexceedthevalues
sponding to a specified classification number) as shown in
listed in Table 6. See test details in Test Method B490.
Table 7.The test is described in detail in the referencedASTM
6.6 p-points—See 3.1.2. designation.
6.7 Coating Thickness:
NOTE 7—There is no direct relation between the results of an acceler-
ated corrosion test and the resistance to corrosion in other media, because
6.7.1 Theminimumcoatingthicknessshallbeasdesignated
several factors, such as the formation of protective films, influence the
by the coating classification number.
progress of corrosion and vary greatly with the conditions encountered.
6.7.2 Itisrecognizedthatrequirementsmayexistforthicker
The results obtained in the test should, therefore, not be regarded as a
coatings than are covered by this specification (see Note 2).
direct guide to the corrosion resistance of the tested materials in all
environments where these materials may be used. Also, performance of
6.7.3 The thickness of a coating and its various layers shall
different materials in the test cannot always be taken as a direct guide to
be measured at points on the significant surfaces (See Section
the relative resistance of these materials in service.
3 and Note 6).
6.8.2 After the article has been subjected to the treatment
NOTE6—Whensignificantsurfacesareinvolvedonwhichthespecified
described in the relevant corrosion test method, it shall be
thickness of deposit cannot readily be controlled, such as threads, holes,
examined for corrosion of the basis metal or blistering of the
deep recesses, bases of angles, and similar areas, the purchaser and the
coating.Any basis metal corrosion or blistering of the coating
manufacturer should recognize the necessity for either thicker deposits on
the more accessible surfaces or for special racking. Special racks may shall be cause for rejection. It is to be understood that
involve the use of conforming, auxiliary, or bipolar electrodes or noncon-
occasional widely scattered, small corrosion defects such as
ducting shields.
surface pits may be observed after the testing period. In
6.7.3.1 The coulometric method described in Test Method general, “acceptable resistance” shall mean that such defects
B504 may be used to measure thickness of the chromium, the are not, when viewed critically, significantly defacing or
B456−17 (2022)
otherwise deleterious to the function of the electroplated part. 6.11.2 Amethodformeasuringthediscontinuities,referred
A method of rating corrosion is given in Practice B537. to as Dubpernell sites, is given in Appendix X4.Amethod for
measuring the number of corrosion sites formed during
NOTE8—Inenvironmentswhereroadsaltssuchascalciumchlorideare
corrosion, referred to as active sites, is given in Appendix X5.
used, a specific type of corrosion has been observed. B995 (Russian Mud
Test) simulates this type of surface corrosion between the top nickel and
chromium deposits. No correlation has yet been established between the
7. Sampling Requirements
test results and actual service performance. The number of hours the test
7.1 The sampling plan used for the inspection of a quantity
is conducted and the results shall be agreed upon between the purchaser
and supplier.
of coated articles shall be as agreed upon by the purchaser and
supplier.
6.8.3 Surface deterioration of the coating itself is expected
to occur during the testing of some types of coatings. The
NOTE 11—Usually, when a collection of coated articles, the inspection
extent to which such surface deterioration will be tolerated
lot, is examined for compliance with the requirements placed on the
shall be specified by the purchaser.
coating, a relatively small number of the articles, the sample, is selected
at random and is inspected. The inspection lot is then classified as
6.9 STEP Test Requirements:
complyingornotcomplyingwiththerequirementsbasedontheresultsof
6.9.1 Theelectrodepotentialdifferencesbetweenindividual the inspection of the sample. The size of the sample and the criteria of
compliance are determined by the application of statistics. The procedure
nickel layers shall be measured for multilayer coatings corre-
is known as sampling inspection. Three standards, Test Method B602,
sponding to SC5, SC4, and SC3 in accordance with Test
Guide B697, and Method B762 contain sampling plans that are designed
Method B764 (STEP Test).
for the sampling inspection of coatings.
6.9.2 The STEP potential difference between the semi-
Test Method B602 contains four sampling plans, three for use with tests
thatarenon-destructiveandonewhentheyaredestructive.Thebuyerand
bright nickel layer and the bright nickel layer has an accepted
seller may agree on the plan or plans to be used. If they do not, Test
range of 100 to 200 mV. For all combinations of nickel layers,
Method B602 identifies the plan to use.
the semi-bright nickel layer is more noble (cathodic) than the
Guide B697 provides a large number of plans and also gives guidance on
bright nickel layer. See Note 9.
theselectionofaplan.WhenGuideB697isspecified,thebuyerandseller
need to agree on the plan to be used.
NOTE 9—For optimum balance between cosmetics and corrosion
Method B762 can be used only for coating requirements that have a
protection, the STEP is recomme
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