ASTM B841-99(2004)
(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)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information.
Designation: B841 – 99 (Reapproved 2004)
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 B568 Test Method for Measurement of Coating Thickness
by X-Ray Spectrometry
1.1 This specification covers the requirements for electrode-
B571 Practice 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
B602 Test Method for Attribute Sampling of Metallic and
standard.
Inorganic Coatings
1.3 The following precautionary statement pertains to the
B697 Guide 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,
B762 Test 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
B849 Specification 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.
B850 Guide for Post-Coating Treatments of Steel for Re-
2. Referenced Documents ducing the Risk of Hydrogen Embrittlement
B3951 Practice for Commercial Packaging
2.1 ASTM Standards:
B117 Practice for Operating Salt Spray (Fog) Apparatus
3. Terminology
B183 Practice for Preparation of Low-Carbon Steel for
3.1 Definitions—Many items used in this specification are
Electroplating
defined in Terminology B374.
B242 Guide 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-
B320 Practice 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.
B322 Guide for Cleaning Metals Prior to Electroplating
Significant surfaces are usually those that are essential to the
B374 Terminology Relating to Electroplating
serviceability or function of the article, or that can be a source
B487 Test Method for Measurement of Metal and Oxide
of corrosion products or tarnish films that interfere with the
CoatingThicknessbyMicroscopicalExaminationofCross
function or desirable appearance of the article.
Section
3.2.2 Discussion—Significant surfaces are those surfaces
B499 Test Method for Measurement of Coating Thick-
that are identified by the purchaser by, for example, indicating
nessesbytheMagneticMethod:NonmagneticCoatingson
them on an engineering drawing of the product or marking a
Magnetic Basis Metals
sample item of the product.
B504 Test Method for Measurement of Thickness of Me-
tallic Coatings by the Coulometric Method
4. Classification
B507 Practice for Design ofArticles to Be Electroplated on
4.1 There is one class of zinc nickel coating defined as
Racks
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 Coatings and is the direct responsibility of Subcommittee
4.2 There are five chromate conversion coating types that
B08.08.04 on Soft Metals.
are defined as follows:
Current edition approved Aug. 1, 2004. Published August 2004. Originally
approved in 1993. Last previous edition approved in 1999 as B841 – 99. DOI:
4.2.1 Type A—With colorless (blue bright) conversion coat-
10.1520/B0841-99R04.
ings,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4.2.2 Type B—With yellow iridescent conversion coatings,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.2.3 Type C—With bronze conversion coatings,
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 – 99 (2004)
4.2.4 Type D—With black chromate conversion coatings, 6.2 Nature of Coating:
and
6.2.1 Thecoatingshallconsistofazincnickelalloythathas
4.2.5 Type E—Any of the above plus organic topcoat.
a minimum of 5 and maximum 12 mass percent nickel, the
balance being zinc.
NOTE 1—Whereas colored chromate conversion coatings are usually
6.2.2 The coating shall be produced from an aqueous
meant to include various shades of yellow to bronze when used with
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.
6.3 Appearance:
4.3 There are three grades according to thickness and are
6.3.1 The coating on all ready visible surfaces shall have an
defined as follows:
acceptable and characteristic appearance as agreed upon by the
Minimum Thickness, µm New ASTM Grade Old ASTM Grade
purchaser and seller. The coating shall be uniform insofar as
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
5.1 In order to make the application of this specification surfaceconditionsofthesubstrate(scratches,pores,rollmarks,
inclusions, and the like) and that persist in the coating despite
complete, the purchaser needs to supply the following infor-
mation to the seller in the purchase order and drawings: the observance of good metal finishing practices shall not be
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,
the as plated state. Flaking shall be cause for rejection in either
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-
NOTE 3—These coatings are commonly used in automotive applica-
strate to be coated,
tions where subsequent forming, bending, and crimping operations are
5.1.4 Location of significant surfaces (see 3.2.1),
commonly performed. These operations will necessarily detract from the
5.1.5 Heat treatment for stress relief, whether it has been
performance of the coatings. While some cracking of coatings will be
unavoidable, flaking of the coating after these subsequent operations shall
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 sub-
6.8),
strate 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
(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. How-
5.1.9 Acceptance inspection procedure to be used (see
ever, these are not normal in the treatment steps preceding the application
Section 8), and of the coating. When they are desired, they are the subject of special
agreement between the purchaser and the seller.
5.1.10 Any requirement for certification (see Section 10).
5.1.11 Anyotheritemsneedingagreement.Forthepurposes
6.4 Thickness:
of this specification, prior agreement on the nature of the finish
6.4.1 The thickness of the coating everywhere on the
is required as items plated in bulk may differ in appearance
significant surfaces as defined in 3.2.1 and shall conform to the
from those that are rack plated.
requirements of the specified grade as defined in 4.3.
6. Coating Requirements NOTE 5—The thickness of electrodeposited coatings varies from point
to point on the surfaces of a product (see Practice B507). The thickness is
6.1 Substrate—The metal to be plated shall be free of flaws
less in interior corners and in holes. Such surfaces are often exempt from
and defects that will be detrimental to the zinc alloy coating. It
thickness requirements. If the full thickness is required in those locations,
shallbesubjectedtosuchcleaning,pickling,andelectroplating
the electroplater will have to use special techniques that will probably
procedures as are necessary to yield deposits with the desired
raise the cost of the process.
quality.
NOTE 6—The coating requirement of this specification is a minimum.
Variationinthethicknessfrompointtopointonanarticleandfromarticle
NOTE 2—Proper preparatory procedures and thorough cleaning are
to article in a production lot is inherent in electroplating. Therefore, if all
essential to ensure satisfactory adhesion and corrosion resistance perfor-
ofthearticlesinaproductionlotaretomeetthethicknessrequirement,the
mance of the coating. Materials used for cleaning should not damage the
average coating thickness for the production lot as a whole will be greater
basis metal, for example by causing defects such as pits, intergranular
than the specified minimum.
attack or stress corrosion cracking. It is recommended that the following
practices for cleaning, where appropriate, be used: Practices B183 and
6.5 Adhesion—Thecoatingshallwithstandnormalhandling
B320, and Guides B242 and B322.
and storage conditions without chipping, flaking,
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