ASTM B841-99
(Specification)Standard Specification for Electrodeposited Coatings for Zinc Nickel Alloy Deposits
Standard Specification for Electrodeposited Coatings for Zinc Nickel Alloy Deposits
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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Designation: B 841 – 99
Standard Specification for
Electrodeposited Coatings of Zinc Nickel Alloy Deposits
This standard is issued under the fixed designation B 841; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope B 602 Test Method of Attribute Sampling of Metallic and
Inorganic Coatings
1.1 This specification covers the requirements for electrode-
B 697 Guide for Selection of Sampling Plans for Inspection
posited zinc nickel alloy coatings on metals.
of Electrodeposited Metallic and Inorganic Coatings
1.2 The values stated in SI units are to be regarded as the
B 762 Method of Variables Sampling of Metallic and Inor-
standard.
ganic Coatings
1.3 The following precautionary statement pertains to the
B 849 Specification for Pretreatments of Iron or Steel for
test method portion only, Section 8, of this specification: This
Reducing Risk of Hydrogen Embrittlement
standard does not purport to address all of the safety concerns,
B 850 Specification for Post-Coating Treatments of Iron or
if any, associated with its use. It is the responsibility of the user
Steel for Reducing Risk of Hydrogen Embrittlement
of this standard to establish appropriate safety and health
B 3951 Practice for Commercial Packaging
practices and determine the applicability of regulatory limita-
tions prior to use.
3. Terminology
2. Referenced Documents 3.1 Definitions—Many items used in this specification are
defined in Terminology B 374.
2.1 ASTM Standards:
3.2 Definitions of Terms Specific to This Standard:
B 117 Practice for Operating Salt Spray (Fog) Apparatus
3.2.1 significant surface, n—that portion of a coated arti-
B 183 Practice for Preparation of Low-Carbon Steel for
cle’s surface where the coating is required to meet all the
Electroplating
requirements of the coating specification for that article.
B 242 Practice for Preparation of High-Carbon Steel for
Significant surfaces are usually those that are essential to the
Electroplating
serviceability or function of the article, or that can be a source
B 320 Practice for Preparation of Iron Castings for Electro-
of corrosion products or tarnish films that interfere with the
plating
function or desirable appearance of the article.
B 322 Practice for Cleaning Metals Prior to Electroplating
3 3.2.2 Discussion—Significant surfaces are those surfaces
B 374 Terminology Relating to Electroplating
that are identified by the purchaser by, for example, indicating
B 487 Test Method for Measurement of Metal and Oxide
them on an engineering drawing of the product or marking a
Coating Thickness by Microscopical Examination of a
sample item of the product.
Cross Section
B 499 Test Method for Measurement of Coating Thick-
4. Classification
nesses By the Magnetic Method: Nonmagnetic Coatings
3 4.1 There is one class of zinc nickel coating defined as
on Magnetic Basis Metals
follows:
B 504 Test Method for Measurement of Thickness of Me-
3 4.1.1 Class 1—Deposits having a minimum of 5 and maxi-
tallic Coatings by the Coulometric Method
mum 12 mass % nickel, the balance being zinc.
B 507 Practice Design of Articles to Be Electroplated on
3 4.2 There are five chromate conversion coating types that
Racks
are defined as follows:
B 568 Test Method for Measurement of Coating Thickness
4.2.1 Type A—With colorless (blue bright) conversion coat-
by X-Ray Spectrometry
3 ings,
B 571 Test Methods for Adhesion of Metallic Coatings
4.2.2 Type B—With yellow iridescent conversion coatings,
4.2.3 Type C—With bronze conversion coatings,
1 4.2.4 Type D—With black chromate conversion coatings,
This specification is under the jurisdiction of ASTM Committee B-8 on
and
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.08.04 on Light Metals.
4.2.5 Type E—Any of the above plus organic topcoat.
Current edition approved Nov. 10, 1999. Published March 2000. Originally
published as B 841 – 93. Last previous edition B 841 – 94.
Annual Book of ASTM Standards, Vol 03.02.
3 4
Annual Book of ASTM Standards, Vol 02.05. Annual Book of ASTM Standards, Vol 15.09.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B 841
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
electroplating system that may be either an alkaline or acid
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 The coating shall have such supplementary conversion
applied to alloyed zinc coatings and are formulated specifically to produce
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:
6.3.1 The coating on all ready visible surfaces shall have an
4.3 There are three grades according to thickness and are
acceptable and characteristic appearance as agreed upon by the
defined as follows:
purchaser and seller. The coating shall be uniform insofar as
Minimum Thickness, μm New ASTM Grade Old ASTM Grade
the basis metal will permit. When the article is to be plated on
55 1
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.
6.3.2 Defects and variations in appearance that arise from
5. Ordering Information
surface conditions of the substrate (scratches, pores, roll marks,
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,
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-
tions where subsequent forming, bending, and crimping operations are
strate to be coated,
commonly performed. These operations will necessarily detract from the
5.1.4 Location of significant surfaces (see 3.2.1),
performance of the coatings. While some cracking of coatings will be
5.1.5 Heat treatment for stress relief, whether it has been
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), unfinished product should provide limits for these defects. A metal finisher
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. How-
8.1.1),
ever, these are not normal in the treatment steps preceding the application
5.1.9 Acceptance inspection procedure to be used (see
of the coating. When they are desired, they are the subject of special
Section 8), and
agreement between the purchaser and the seller.
5.1.10 Any requirement for certification (see Section 10).
6.4 Thickness:
5.1.11 Any other items needing agreement. For the purposes
6.4.1 The thickness of the coating everywhere on the
of this specification, prior agreement on the nature of the finish
is required as items plated in bulk may differ in appearance significant surfaces as defined in 3.2.1 and shall conform to the
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 B 507). The thickness
6.1 Substrate—The metal to be plated shall be free of flaws
is less in interior corners and in holes. Such surfaces are often exempt
and defects that will be detrimental to the zinc alloy coating. It
from thickness requirements. If the full thickness is required in those
shall be subjected to such cleaning, pickling, and electroplating locations, the electroplater will have to use special techniques that will
probably 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.
quality.
Variation in the thickness from point to point on an article and from article
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-
of the articles in a production lot are to meet the thickness requirement, 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
6.5 Adhesion—The coating shall withstand normal handling
practices for cleaning, where appropriate, be used: Practices B 183, B 242,
B 320 and B 322.
and storage conditions without chipping, flaking, or other
coating damage and shall conform to the minimum require-
6.1.1 The electroplating shall be applied after all basis metal
ments set forth in Section 8.
heat treatments have
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