ASTM B841-18

Standard Specification for Electrodeposited Coatings of Zinc Nickel Alloy Deposits

ABSTRACT
This specification covers the requirements for electrodeposited zinc nickel alloy coatings on metals. The zinc nickel coating shall be defined as Class 1. The five chromate conversion coating types shall be defined as follows: Type A shall be with colorless conversion coatings, Type B shall be with yellow iridescent conversion coatings, Type C shall be with bronze conversion coatings, Type D shall be with black chromate conversion coatings, and Type E shall be with any colors mentioned plus organic topcoat. The metal to be plated shall be free of flaws and defects that will be detrimental to the zinc alloy coating. It shall be subjected to such cleaning, pickling, and electroplating procedures as necessary to yield deposits. The coating shall be produced from an aqueous electroplating system that may be either an alkaline or acid formulation. The coating on all ready visible surfaces shall have an acceptable and characteristic appearance. The coating shall be adherent, free from blisters, pits, or discontinuities, and shall be free of cracks in the as plated state. The coating shall withstand normal handling and storage conditions without chipping, flaking, or other coating damage. The corrosion resistance of the coating shall be evaluated.
SCOPE
1.1 This specification covers the requirements for electrodeposited zinc nickel alloy coatings on metals.  
1.2 The values stated in SI units are to be regarded as the standard.  
1.3 The following precautionary statement pertains to the test method portion only, Section 8, of this specification: 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.  
1.4 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

• Status: Published
• Publication Date: 30-Jun-2018
• ICS: 25.220.40 - Metallic coatings
• ICS: 77.120.40 - Nickel, chromium and their alloys
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.06 - Soft Metals

Relations

• Replaces: ASTM B841-99(2010) - Standard Specification for Electrodeposited Coatings for Zinc Nickel Alloy Deposits
• Effective Date: 01-Jul-2018
• Refers: ASTM B849-02(2023) - Standard Specification for Pre-Treatments of Iron or Steel for Reducing Risk of Hydrogen Embrittlement
• Effective Date: 01-Nov-2023
• Refers: ASTM B571-23 - Standard Practice for Qualitative Adhesion Testing of Metallic Coatings
• Effective Date: 01-Nov-2023
• Refers: ASTM B320-60(2019) - Standard Practice for Preparation of Iron Castings for Electroplating
• Effective Date: 01-Apr-2019
• Refers: ASTM B849-02(2019) - Standard Specification for Pre-Treatments of Iron or Steel for Reducing Risk of Hydrogen Embrittlement
• Effective Date: 01-Apr-2019
• Refers: ASTM B571-18 - Standard Practice for Qualitative Adhesion Testing of Metallic Coatings
• Effective Date: 01-Aug-2018
• Refers: ASTM B242-99(2014) - Standard Guide for Preparation of High-Carbon Steel for Electroplating
• Effective Date: 01-Nov-2014
• Refers: ASTM B183-79(2014) - Standard Practice for Preparation of Low-Carbon Steel for Electroplating
• Effective Date: 01-Nov-2014
• Refers: ASTM B320-60(2013) - Standard Practice for Preparation of Iron Castings for Electroplating
• Effective Date: 01-Dec-2013
• Refers: ASTM B571-97(2013) - Standard Practice for Qualitative Adhesion Testing of Metallic Coatings
• Effective Date: 01-Dec-2013
• Refers: ASTM B849-02(2013) - Standard Specification for Pre-Treatments of Iron or Steel for Reducing Risk of Hydrogen Embrittlement
• Effective Date: 01-May-2013
• Refers: ASTM B504-90(2011) - Standard Test Method for Measurement of Thickness of Metallic Coatings by the Coulometric Method
• Effective Date: 01-Oct-2011
• Refers: ASTM B117-11 - Standard Practice for Operating Salt Spray (Fog) Apparatus
• Effective Date: 01-Oct-2011
• Refers: ASTM B374-06(2011) - Standard Terminology Relating to Electroplating
• Effective Date: 01-Apr-2011
• Refers: ASTM B697-88(2010) - Standard Guide for Selection of Sampling Plans for Inspection of Electrodeposited Metallic and Inorganic Coatings
• Effective Date: 01-Apr-2010

Overview

ASTM B841-18: Standard Specification for Electrodeposited Coatings of Zinc Nickel Alloy Deposits defines requirements for the electrodeposition of zinc-nickel alloy coatings on various metal substrates. This international standard published by ASTM International ensures high performance in corrosion resistance for parts requiring enhanced protection and reliability. The specification covers coating classes, chromate conversion types, thickness grades, appearance, adhesion, and test methods, supporting quality assurance across industries such as automotive, electronics, and heavy equipment manufacturing.

Key Topics

• Coating Classes and Composition
  • Class 1: Zinc-nickel coatings with 5-12% nickel content.
  • Class 2: Zinc-nickel coatings with 12-16% nickel content.
• Chromate Conversion Coating Types
  • Type A: Colorless (blue-bright) conversion coatings
  • Type B: Yellow iridescent conversion coatings
  • Type C: Bronze conversion coatings
  • Type D: Black chromate conversion coatings
  • Type E: Any above, plus organic topcoat
• Grades by Coating Thickness
  • Minimum thicknesses: 5 μm, 8 μm, and 10 μm, assigned as Grades 5, 8, and 10
• Substrate Preparation
  • Surfaces must be free from detrimental flaws or defects
  • Cleaning and pre-treatment follow referenced ASTM practices
• Appearance and Surface Quality
  • Coating must be visually uniform, free from blisters, pits, discontinuities, cracks, or flaking
  • Significant surfaces for coating quality identified by purchaser
• Corrosion Resistance
  • Assessment often uses neutral salt spray testing (ASTM B117)
• Adhesion Requirements
  • Coatings must withstand normal handling and storage without chipping or flaking
• Process and Test Methods
  • Electroplating may use alkaline or acid formulations
  • Quality controls involve thickness measurements, adhesion tests, and corrosion resistance checks

Applications

ASTM B841-18 is widely referenced for specifying zinc-nickel alloy coatings in applications where superior corrosion protection and coating durability are necessary:

• Automotive components: Used for fasteners, brackets, and chassis parts to improve resistance to rust and extend service life under harsh conditions
• Electronics and electrical hardware: Protects connectors and terminal blocks from oxidation and environmental degradation
• General industrial fabrication: Applied to heavy equipment, tools, and structural steel elements exposed to moisture, salts, or chemicals
• Aerospace and military hardware: Enhances longevity and reliability of mission-critical parts

Proper implementation of this standard supports reduced maintenance costs, improved safety, and extended product lifespans by delivering robust corrosion resistant coatings.

Related Standards

For full compliance and best practice applications, ASTM B841-18 references several other key ASTM standards, including:

• ASTM B117: Practice for Operating Salt Spray (Fog) Apparatus, used for corrosion testing
• ASTM B183, B242, B320, B322: Practices and guides for substrate cleaning and preparation prior to electroplating
• ASTM B374: Terminology relating to electroplating
• ASTM B487, B499, B504, B568: Standard test methods for measuring coating thickness
• ASTM B571: Test method for adhesion of metallic coatings
• ASTM B849, B850: Specifications for pre- and post-coating treatments to reduce risk of hydrogen embrittlement

Consulting these related standards ensures comprehensive quality control and consistency for zinc-nickel electroplated coatings in accordance with ASTM B841-18.

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Keywords: ASTM B841-18, zinc-nickel alloy coatings, electrodeposited coatings, corrosion resistant coatings, chromate conversion coating, electroplating, automotive coatings, industrial coatings, ASTM standards.

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: B841 −18
Standard Specification for
Electrodeposited Coatings of Zinc Nickel Alloy Deposits
This standard is issued under the fixed designation B841; 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.
1. Scope B499Test Method for Measurement of CoatingThicknesses
by the Magnetic Method: Nonmagnetic Coatings on
1.1 Thisspecificationcoverstherequirementsforelectrode-
Magnetic Basis Metals
posited zinc nickel alloy coatings on metals.
B504Test Method for Measurement of Thickness of Metal-
1.2 The values stated in SI units are to be regarded as the
lic Coatings by the Coulometric Method
standard.
B507Practice for Design ofArticles to Be Electroplated on
1.3 The following precautionary statement pertains to the
Racks
test method portion only, Section 8, of this specification: This B568Test Method for Measurement of Coating Thickness
standard does not purport to address all of the safety concerns,
by X-Ray Spectrometry
if any, associated with its use. It is the responsibility of the user B571Practice for Qualitative Adhesion Testing of Metallic
of this standard to establish appropriate safety, health, and
Coatings
environmental practices and determine the applicability of B602Test Method for Attribute Sampling of Metallic and
regulatory limitations prior to use.
Inorganic Coatings
1.4 This international standard was developed in accor- B697Guide for Selection of Sampling Plans for Inspection
dance with internationally recognized principles on standard-
of Electrodeposited Metallic and Inorganic Coatings
ization established in the Decision on Principles for the B762Test Method of Variables Sampling of Metallic and
Development of International Standards, Guides and Recom-
Inorganic Coatings
mendations issued by the World Trade Organization Technical B849Specification for Pre-Treatments of Iron or Steel for
Barriers to Trade (TBT) Committee.
Reducing Risk of Hydrogen Embrittlement
B850GuideforPost-CoatingTreatmentsofSteelforReduc-
2. Referenced Documents
ing the Risk of Hydrogen Embrittlement
D3951Practice for Commercial Packaging
2.1 ASTM Standards:
B117Practice for Operating Salt Spray (Fog) Apparatus
3. Terminology
B183Practice for Preparation of Low-Carbon Steel for
3.1 Definitions—Many items used in this specification are
Electroplating
defined in Terminology B374.
B242Guide for Preparation of High-Carbon Steel for Elec-
troplating 3.2 Definitions of Terms Specific to This Standard:
3.2.1 significant surface, n—that portion of a coated arti-
B320Practice for Preparation of Iron Castings for Electro-
plating cle’s surface where the coating is required to meet all the
B322Guide for Cleaning Metals Prior to Electroplating requirements of the coating specification for that article.
B374Terminology Relating to Electroplating Significant surfaces are usually those that are essential to the
B487Test Method for Measurement of Metal and Oxide serviceability or function of the article, or that can be a source
Coating Thickness by Microscopical Examination of of corrosion products or tarnish films that interfere with the
Cross Section function or desirable appearance of the article.
3.2.2 Discussion—Significant surfaces are those surfaces
that are identified by the purchaser by, for example, indicating
This specification is under the jurisdiction of ASTM Committee B08 on
them on an engineering drawing of the product or marking a
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
sample item of the product.
B08.06 on Soft Metals.
CurrenteditionapprovedJuly1,2018.PublishedJuly2018.Originallyapproved
4. Classification
in 1993. Last previous edition approved in 2018 as B841–99(2018). DOI:
10.1520/B0841-18.
4.1 There are two classes of zinc nickel coating defined as
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
follows:
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
4.1.1 Class 1—Deposits having a minimum of 5 and maxi-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. mum 12 mass % nickel, the balance being zinc.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B841 − 18
4.1.2 Class 2—Deposits having a minimum of 12 and shallbesubjectedtosuchcleaning,pickling,andelectroplating
maximum 16 mass % nickel, the balance being zinc. procedures as are necessary to yield deposits with the desired
quality.
4.2 There are five chromate conversion coating or passiva-
tion types that are defined as follows: NOTE 2—Proper preparatory procedures and thorough cleaning are
essential to ensure satisfactory adhesion and corrosion resistance perfor-
Conversion Designation
mance of the coating. Materials used for cleaning should not damage the
Type Description Hexavalent Non-Hexavalent
basis metal, for example by causing defects such as pits, intergranular
Chromium Chromium
attack or stress corrosion cracking. It is recommended that the following
Type A Colorless (Blue AAN
Bright) Conversion practices for cleaning, where appropriate, be used: Practices B183 and
Type B Yellow Iridescent BBN B320, and Guides B242 and B322.
Conversion
6.1.1 Theelectroplatingshallbeappliedafterallbasismetal
Type C Bronze Conversion C CN
Type D Black Chromate DDN
heat treatments have been completed.
Conversion
6.2 Nature of Coating:
Type E Any of the above E
plus organic topcoat
6.2.1 The zinc-nickel alloy plate shall consist of a compo-
sitionconformingtotherequirementscalledoutinsection4.1.
NOTE 1—Whereas colored chromate conversion coatings are usually
meant to include various shades of yellow to bronze when used with 6.2.2 The coating shall be produced from an aqueous
nonalloyed zinc, yellow and bronze chromate conversion coatings are
electroplating system that may be either an alkaline or acid
considered distinctly different in appearance and performance when
formulation as specified by the purchaser.
appliedtoalloyedzinccoatingsandareformulatedspecificallytoproduce
6.2.3 Thecoatingshallhavesuchsupplementaryconversion
the desired coating and are formulated specifically to produce the desired
coatings as defined in 4.2 and specified in the purchase order.
coating.
4.3 There are three grades according to thickness and are 6.3 Appearance:
6.3.1 Thecoatingonallreadyvisiblesurfacesshallhavean
defined as follows:
acceptableandcharacteristicappearanceasagreeduponbythe
Minimum Thickness, µm New ASTM Grade Old ASTM Grade
55 1 purchaser and seller. The coating shall be uniform insofar as
88 2
the basis metal will permit. When the article is to be plated on
10 10 3
a rack, contact marks may be unavoidable. Location of such
marks(s) shall be indicated on the article or its drawing.
5. Ordering Information
6.3.2 Defects and variations in appearance that arise from
5.1 In order to make the application of this specification
surfaceconditionsofthesubstrate(scratches,pores,rollmarks,
complete, the purchaser needs to supply the following infor-
inclusions, and the like) and that persist in the coating despite
mation to the seller in the purchase order and drawings:
the observance of good metal finishing practices shall not be
5.1.1 Title,ASTM designation number, and date of issue of
cause for rejection. The coating shall be adherent, free from
this standard specification,
blisters,pits,discontinuities,orcombinationsthereof,andshall
5.1.2 Deposit by classification including Class, Type, and
be free of cracks in the as plated state. Flaking shall be cause
Grade (see 4.1, 4.2, 4.3),
for rejection in either the as plated state or after subsequent
5.1.3 Composition and metallurgical condition of the sub-
operations.
strate to be coated,
NOTE3—Thesecoatingsarecommonlyusedinautomotiveapplications
5.1.4 Location of significant surfaces (see 3.2.1),
where subsequent forming, bending, and crimping operations are com-
5.1.5 Heat treatment for stress relief, whether it has been monly performed. These operations will necessarily detract from the
performance of the coatings. While some cracking of coatings will be
performed by purchaser or is required (see 6.7),
unavoidable,flakingofthecoatingafterthesesubsequentoperationsshall
5.1.6 Heat treatment after electroplating, if required (see
be cause for rejection.
6.8),
NOTE 4—Coatings generally perform better in service when the
5.1.7 Whether or not location of rack marks is to be defined substrate over which they are applied is smooth and free of torn metal,
inclusions, pores, and other defects. The specifications covering the
(see 6.3.1),
unfinishedproductshouldprovidelimitsforthesedefects.Ametalfinisher
5.1.8 Any requirement for special test specimens (see
can often remove defects through special treatments, such as grinding,
8.1.1),
polishing, abrasive blasting, chemical etches, and electropolishing.
However, these are not normal in the treatment steps preceding the
5.1.9 Acceptance inspection procedure to be used (see
application of the coating. When they are desired, they are the subject of
Section 8), and
special agreement between the purchaser and the seller.
5.1.10 Any requirement for certification (see Section 10).
6.4 Thickness:
5.1.11 Anyotheritemsneedingagreement.Forthepurposes
6.4.1 The thickness of the coating everywhere on the
ofthisspecification,prioragreementonthenatureofthefinish
significantsurfacesasdefinedin3.2.1andshallconformtothe
is required as items plated in bulk may differ in appearance
requirements of the specified grade as defined in 4.3.
from those that are rack plated.
NOTE 5—The thickness of electrodeposited coatings varies from point
6. Coating Requirements to point on the surfaces of a product (see Practice B507).The thickness is
less in interior corners and in holes. Such surfaces are often exempt from
6.1 Substrate—The metal to be plated shall be free of flaws
thickness requirements. If the full thickness is required in those locations,
and defects that will be detrimental to the zinc alloy coating. It the electroplater will have to use special techniques that will probably
B841 − 18
raise the cost of the process. beusedsothatthepropersamplingplanisselected.Atestmaydestroythe
NOTE 6—The coating requirement of this specification is a minimum. coating but in a noncritical area; or, although it may destroy the coating,
Variationinthethicknessfrompointtopointonanarticleandfromarticle a teste
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: B841 − 99 (Reapproved 2010) B841 − 18
Standard Specification for
Electrodeposited Coatings of Zinc Nickel Alloy Deposits
This standard is issued under the fixed designation B841; 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.
1. Scope
1.1 This specification covers the requirements for electrodeposited zinc nickel alloy coatings on metals.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 The following precautionary statement pertains to the test method portion only, Section 8, of this specification: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 safety, health, and healthenvironmental practices and determine the applicability of
regulatory limitations prior to use.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
B117 Practice for Operating Salt Spray (Fog) Apparatus
B183 Practice for Preparation of Low-Carbon Steel for Electroplating
B242 Guide for Preparation of High-Carbon Steel for Electroplating
B320 Practice for Preparation of Iron Castings for Electroplating
B322 Guide for Cleaning Metals Prior to Electroplating
B374 Terminology Relating to Electroplating
B487 Test Method for Measurement of Metal and Oxide Coating Thickness by Microscopical Examination of Cross Section
B499 Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings on Magnetic Basis
Metals
B504 Test Method for Measurement of Thickness of Metallic Coatings by the Coulometric Method
B507 Practice for Design of Articles to Be Electroplated on Racks
B568 Test Method for Measurement of Coating Thickness by X-Ray Spectrometry
B571 Practice for Qualitative Adhesion Testing of Metallic Coatings
B602 Test Method for Attribute Sampling of Metallic and Inorganic Coatings
B697 Guide for Selection of Sampling Plans for Inspection of Electrodeposited Metallic and Inorganic Coatings
B762 Test Method of Variables Sampling of Metallic and Inorganic Coatings
B849 Specification for Pre-Treatments of Iron or Steel for Reducing Risk of Hydrogen Embrittlement
B850 Guide for Post-Coating Treatments of Steel for Reducing the Risk of Hydrogen Embrittlement
D3951 Practice for Commercial Packaging
3. Terminology
3.1 Definitions—Many items used in this specification are defined in Terminology B374.
3.2 Definitions of Terms Specific to This Standard:
This specification is under the jurisdiction of ASTM Committee B08 on Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee B08.06 on Soft
Metals.
Current edition approved Jan. 1, 2010July 1, 2018. Published February 2010July 2018. Originally approved in 1993. Last previous edition approved in 120042018 as
B841 – 99(2004).(2018). DOI: 10.1520/B0841-99R09.10.1520/B0841-18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B841 − 18
3.2.1 significant surface, n—that portion of a coated article’s surface where the coating is required to meet all the requirements
of the coating specification for that article. Significant surfaces are usually those that are essential to the serviceability or function
of the article, or that can be a source of corrosion products or tarnish films that interfere with the function or desirable appearance
of the article.
3.2.2 Discussion—Significant surfaces are those surfaces that are identified by the purchaser by, for example, indicating them
on an engineering drawing of the product or marking a sample item of the product.
4. Classification
4.1 There is one classare two classes of zinc nickel coating defined as follows:
4.1.1 Class 1—Deposits having a minimum of 5 and maximum 12 mass % nickel, the balance being zinc.
4.1.2 Class 2—Deposits having a minimum of 12 and maximum 16 mass % nickel, the balance being zinc.
4.2 There are five chromate conversion coating or passivation types that are defined as follows:
Conversion Designation
Type Description Hexavalent Chromium Non-Hexavalent Chromium
Type A Colorless (Blue Bright) Conversion A AN
Type B Yellow Iridescent Conversion B BN
Type C Bronze Conversion C CN
Type D Black Chromate Conversion D DN
Type E Any of the above plus organic topcoat E
4.2.1 Type A—With colorless (blue bright) conversion coatings,
NOTE 1—Whereas colored chromate conversion coatings are usually meant to include various shades of yellow to bronze when used with nonalloyed
zinc, yellow and bronze chromate conversion coatings are considered distinctly different in appearance and performance when applied to alloyed zinc
coatings and are formulated specifically to produce the desired coating and are formulated specifically to produce the desired coating.
4.2.2 Type B—With yellow iridescent conversion coatings,
4.2.3 Type C—With bronze conversion coatings,
4.2.4 Type D—With black chromate conversion coatings, and
4.2.5 Type E—Any of the above plus organic topcoat.
NOTE 1—Whereas colored chromate conversion coatings are usually meant to include various shades of yellow to bronze when used with nonalloyed
zinc, yellow and bronze chromate conversion coatings are considered distinctly different in appearance and performance when applied to alloyed zinc
coatings and are formulated specifically to produce the desired coating and are formulated specifically to produce the desired coating.
4.3 There are three grades according to thickness and are defined as follows:
Minimum Thickness, μm New ASTM Grade Old ASTM Grade
5 5 1
8 8 2
10 10 3
5. Ordering Information
5.1 In order to make the application of this specification complete, the purchaser needs to supply the following information to
the seller in the purchase order and drawings:
5.1.1 Title, ASTM designation number, and date of issue of this standard specification,
5.1.2 Deposit by classification including Class, Type, and Grade (see 4.1, 4.2, 4.3),
5.1.3 Composition and metallurgical condition of the substrate to be coated,
5.1.4 Location of significant surfaces (see 3.2.1),
5.1.5 Heat treatment for stress relief, whether it has been performed by purchaser or is required (see 6.7),
5.1.6 Heat treatment after electroplating, if required (see 6.8),
5.1.7 Whether or not location of rack marks is to be defined (see 6.3.1),
5.1.8 Any requirement for special test specimens (see 8.1.1),
5.1.9 Acceptance inspection procedure to be used (see Section 8), and
5.1.10 Any requirement for certification (see Section 10).
5.1.11 Any other items needing agreement. For the purposes of this specification, prior agreement on the nature of the finish
is required as items plated in bulk may differ in appearance from those that are rack plated.
6. Coating Requirements
6.1 Substrate—The metal to be plated shall be free of flaws and defects that will be detrimental to the zinc alloy coating. It shall
be subjected to such cleaning, pickling, and electroplating procedures as are necessary to yield deposits with the desired quality.
NOTE 2—Proper preparatory procedures and thorough cleaning are essential to ensure satisfactory adhesion and corrosion resistance performance of
the coating. Materials used for cleaning should not damage the basis metal, for example by causing defects such as pits, intergranular attack or stress
corrosion cracking. It is recommended that the following practices for cleaning, where appropriate, be used: Practices B183 and B320, and Guides B242
and B322.
B841 − 18
6.1.1 The electroplating shall be applied after all basis metal heat treatments have been completed.
6.2 Nature of Coating:
6.2.1 The coating zinc-nickel alloy plate shall consist of a zinc nickel alloy that has a minimum of 5 and maximum 12 mass
percent nickel, the balance being zinc.composition conforming to the requirements called out in section 4.1.
6.2.2 The coating shall be produced from an aqueous electroplating system that may be either an alkaline or acid formulation
as specified by the purchaser.
6.2.3 The coating shall have such supplementary conversion coatings as defined in 4.2 and specified in the purchase order.
6.3 Appearance:
6.3.1 The coating on all ready visible surfaces shall have an acceptable and characteristic appearance as agreed upon by the
purchaser and seller. The coating shall be uniform insofar as the basis metal will permit. When the article is to be plated on a rack,
contact marks may be unavoidable. Location of such marks(s) shall be indicated on the article or its drawing.
6.3.2 Defects and variations in appearance that arise from surface conditions of the substrate (scratches, pores, roll marks,
inclusions, and the like) and that persist in the coating despite the observance of good metal finishing practices shall not be cause
for rejection. The coating shall be adherent, free from blisters, pits, discontinuities, or discontinuities, combinations thereof, and
shall be free of cracks in the as plated state. Flaking shall be cause for rejection in either the as plated state or after subsequent
operations.
NOTE 3—These coatings are commonly used in automotive applications where subsequent forming, bending, and crimping operations are commonly
performed. These operations will necessarily detract from the performance of the coatings. While some cracking of coatings will be unavoidable, flaking
of the coating after these subsequent operations shall be cause for rejection.
NOTE 4—Coatings generally perform better in service when the substrate over which they are applied is smooth and free of torn metal, inclusions, pores,
and other defects. The specifications covering the unfinished product should provide limits for these defects. A metal finisher can often remove defects
through special treatments, such as grinding, polishing, abrasive blasting, chemical etches, and electropolishing. However, these are not normal in the
treatment steps preceding the application of the coating. When they are desired, they are the subject of special agreement between the purchaser and the
seller.
6.4 Thickness:
6.4.1 The thickness of the coating everywhere on the significant surfaces as defined in 3.2.1 and shall conform to the
requirements of the specified grade as defined in 4.3.
NOTE 5—The thickness of electrodeposited coatings varies from point to point on the surfaces of a product (see Practice B507). The thickness is less
in interior corners and in holes. Such surfaces are often exempt from thickness requiremen
...