ASTM B841-99(2010)
(Specification)Standard Specification for Electrodeposited Coatings for Zinc Nickel Alloy Deposits
Standard Specification for Electrodeposited Coatings for 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation:B841 −99(Reapproved 2010)
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 B568Test Method for Measurement of Coating Thickness
by X-Ray Spectrometry
1.1 Thisspecificationcoverstherequirementsforelectrode-
B571Practice for Qualitative Adhesion Testing of Metallic
posited zinc nickel alloy coatings on metals.
Coatings
1.2 The values stated in SI units are to be regarded as the
B602Test Method for Attribute Sampling of Metallic and
standard.
Inorganic Coatings
1.3 The following precautionary statement pertains to the
B697Guide for Selection of Sampling Plans for Inspection
test method portion only, Section 8, of this specification: This of Electrodeposited Metallic and Inorganic Coatings
standard does not purport to address all of the safety concerns,
B762Test Method of Variables Sampling of Metallic and
if any, associated with its use. It is the responsibility of the user Inorganic Coatings
of this standard to establish appropriate safety and health
B849Specification for Pre-Treatments of Iron or Steel for
practices and determine the applicability of regulatory limita- Reducing Risk of Hydrogen Embrittlement
tions prior to use.
B850GuideforPost-CoatingTreatmentsofSteelforReduc-
ing the Risk of Hydrogen Embrittlement
2. Referenced Documents
D3951Practice for Commercial Packaging
2.1 ASTM Standards:
3. Terminology
B117Practice for Operating Salt Spray (Fog) Apparatus
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-
3.2 Definitions of Terms Specific to This Standard:
troplating
3.2.1 significant surface, n—that portion of a coated arti-
B320Practice for Preparation of Iron Castings for Electro-
cle’s surface where the coating is required to meet all the
plating
requirements of the coating specification for that article.
B322Guide for Cleaning Metals Prior to Electroplating
Significant surfaces are usually those that are essential to the
B374Terminology Relating to Electroplating
serviceability or function of the article, or that can be a source
B487Test Method for Measurement of Metal and Oxide
of corrosion products or tarnish films that interfere with the
Coating Thickness by Microscopical Examination of
function or desirable appearance of the article.
Cross Section
3.2.2 Discussion—Significant surfaces are those surfaces
B499Test Method for Measurement of CoatingThicknesses
that are identified by the purchaser by, for example, indicating
by the Magnetic Method: Nonmagnetic Coatings on
them on an engineering drawing of the product or marking a
Magnetic Basis Metals
sample item of the product.
B504Test Method for Measurement of Thickness of Metal-
lic Coatings by the Coulometric Method
4. Classification
B507Practice for Design ofArticles to Be Electroplated on
Racks 4.1 There is one class of zinc nickel coating defined as
follows:
4.1.1 Class 1—Deposits having a minimum of 5 and maxi-
This specification is under the jurisdiction of ASTM Committee B08 on
mum 12 mass % nickel, the balance being zinc.
Metallic and Inorganic Coatingsand is the direct responsibility of Subcommittee
B08.06 on Soft Metals.
4.2 There are five chromate conversion coating types that
Current edition approved Jan. 1, 2010. Published February 2010. Originally
are defined as follows:
approved in 1993. Last previous edition approved in 12004 as B841–99(2004).
DOI: 10.1520/B0841-99R09.
4.2.1 Type A—With colorless (blue bright) conversion
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
coatings,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.2.2 Type B—With yellow iridescent conversion coatings,
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 4.2.3 Type C—With bronze conversion coatings,
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B841−99(2010)
4.2.4 Type D—With black chromate conversion coatings, 6.2.1 Thecoatingshallconsistofazincnickelalloythathas
and a minimum of 5 and maximum 12 mass percent nickel, the
4.2.5 Type E—Any of the above plus organic topcoat. balance being zinc.
6.2.2 The coating shall be produced from an aqueous
NOTE 1—Whereas colored chromate conversion coatings are usually
electroplating system that may be either an alkaline or acid
meant to include various shades of yellow to bronze when used with
nonalloyed zinc, yellow and bronze chromate conversion coatings are formulation as specified by the purchaser.
considered distinctly different in appearance and performance when
6.2.3 Thecoatingshallhavesuchsupplementaryconversion
appliedtoalloyedzinccoatingsandareformulatedspecificallytoproduce
coatings as defined in 4.2 and specified in the purchase order.
the desired coating and are formulated specifically to produce the desired
coating.
6.3 Appearance:
4.3 There are three grades according to thickness and are 6.3.1 Thecoatingonallreadyvisiblesurfacesshallhavean
defined as follows: acceptableandcharacteristicappearanceasagreeduponbythe
purchaser and seller. The coating shall be uniform insofar as
Minimum Thickness, µm New ASTM Grade Old ASTM Grade
55 1
the basis metal will permit. When the article is to be plated on
88 2
a rack, contact marks may be unavoidable. Location of such
10 10 3
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
surfaceconditionsofthesubstrate(scratches,pores,rollmarks,
5.1 In order to make the application of this specification
inclusions, and the like) and that persist in the coating despite
complete, the purchaser needs to supply the following infor-
the observance of good metal finishing practices shall not be
mation to the seller in the purchase order and drawings:
cause for rejection. The coating shall be adherent, free from
5.1.1 Title,ASTM designation number, and date of issue of
blisters, pits, or discontinuities, and shall be free of cracks in
this standard specification,
theasplatedstate.Flakingshallbecauseforrejectionineither
5.1.2 Deposit by classification including Class, Type, and
the as plated state or after subsequent operations.
Grade (see 4.1, 4.2, 4.3),
5.1.3 Composition and metallurgical condition of the sub-
NOTE3—Thesecoatingsarecommonlyusedinautomotiveapplications
strate to be coated,
where subsequent forming, bending, and crimping operations are com-
5.1.4 Location of significant surfaces (see 3.2.1),
monly performed. These operations will necessarily detract from the
performance of the coatings. While some cracking of coatings will be
5.1.5 Heat treatment for stress relief, whether it has been
unavoidable,flakingofthecoatingafterthesesubsequentoperationsshall
performed by purchaser or is required (see 6.7),
be cause for rejection.
5.1.6 Heat treatment after electroplating, if required (see
NOTE 4—Coatings generally perform better in service when the
6.8),
substrate over which they are applied is smooth and free of torn metal,
5.1.7 Whether or not location of rack marks is to be defined
inclusions, pores, and other defects. The specifications covering the
unfinishedproductshouldprovidelimitsforthesedefects.Ametalfinisher
(see 6.3.1),
can often remove defects through special treatments, such as grinding,
5.1.8 Any requirement for special test specimens (see
polishing, abrasive blasting, chemical etches, and electropolishing.
8.1.1),
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
shallbesubjectedtosuchcleaning,pickling,andelectroplating
raise the cost of the process.
procedures as are necessary to yield deposits with the desired
NOTE 6—The coating requirement of this specification is a minimum.
Variationinthethicknessfrompointtopointonanarticleandfromarticle
quality.
to article in a production lot is inherent in electroplating. Therefore, if all
NOTE 2—Proper preparatory procedures and thorough cleaning are
ofthearticlesinaproductionlotaretomeetthethicknessrequirement,the
essential to ensure satisfactory adhesion and corrosion resistance perfor-
averagecoatingthicknessfortheproductionlotasawholewillbegreater
mance of the coating. Materials used for cleaning should not damage the
than the specified minimum.
basis metal, for example by causing defects such as pits, intergranular
6.5 Adhesion—Thecoatingshallwithstandnormalhandling
attack or stress corrosion cracking. It is recommended that the following
practices for cleaning, where appropriate, be used: Practices B183 and and storage conditions without chipping, flaking, or other
B320, and Guides B242 and B322.
coating damage and shall confor
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