ASTM B605-95a(2004)
(Specification)Standard Specification for Electrodeposited Coatings of Tin-Nickel Alloy
Standard Specification for Electrodeposited Coatings of Tin-Nickel Alloy
ABSTRACT
This specification establishes the requirements for electrodeposited tin-nickel alloy coatings from aqueous solutions intended for the corrosion protection of fabricated articles of iron, steel, zinc-base alloys, copper, and copper alloys. This specification does not apply to sheets, strips, or wires in the fabricated form. It also may not be applicable to finely threaded articles, but the decision to use the coating on such components may be made by the purchaser. Coating grades shall be designated by a service condition number, which indicates the severity of exposure for which the coating is intended, and a coating thickness notation. Iron and steel specimens shall undergo pre- and post-coating treatments for reducing the risk of hydrogen embrittlement. Coatings shall be sampled, tested, and conform to specified requirements as to appearance (visible defects), composition, thickness (assessed either by microscopical, magnetic, coulometric, beta backscatter, or X-ray spectrometry), adhesion (determined either by burnishing, or heat-quench test), and integrity (including gross defects, mechanical damage, and porosity).
SCOPE
1.1 This specification covers the requirements for electrodeposited tin-nickel alloy coatings from aqueous solutions intended for the corrosion protection of fabricated articles of iron, steel, zinc-base alloys, copper, and copper alloys. The composition of the alloy remains constant at 65/35 tin-nickel in spite of wide fluctuations in both composition and operating conditions. The composition corresponds quite closely to an equiatomic ratio, and the process favors the co-deposition of tin and nickel atoms at identical rates.
1.2 This specification does not apply to sheet, strip, or wire in the fabricated form. It also may not be applicable to threaded articles having basic major diameters up to and including 19 mm because of the nonuniformity of thickness that can be expected on fine threads. However, a decision to use the coating on such components may be made by the purchaser.
1.3 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: B605 – 95a (Reapproved 2004)
Standard Specification for
Electrodeposited Coatings of Tin-Nickel Alloy
This standard is issued under the fixed designation B605; 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 B374 Terminology Relating to Electroplating
B487 Test Method for Measurement of Metal and Oxide
1.1 This specification covers the requirements for electrode-
CoatingThicknessbyMicroscopicalExaminationofCross
posited tin-nickel alloy coatings from aqueous solutions in-
Section
tended for the corrosion protection of fabricated articles of
B499 Test Method for Measurement of Coating Thick-
iron, steel, zinc-base alloys, copper, and copper alloys. The
nessesbytheMagneticMethod:NonmagneticCoatingson
compositionofthealloyremainsconstantat65/35tin-nickelin
Magnetic Basis Metals
spite of wide fluctuations in both composition and operating
B504 Test Method for Measurement of Thickness of Me-
conditions. The composition corresponds quite closely to an
tallic Coatings by the Coulometric Method
equiatomic ratio, and the process favors the co-deposition of
B507 Practice for Design ofArticles to Be Electroplated on
tin and nickel atoms at identical rates.
Racks
1.2 This specification does not apply to sheet, strip, or wire
B567 Test Method for Measurement of Coating Thickness
inthefabricatedform.Italsomaynotbeapplicabletothreaded
by the Beta Backscatter Method
articles having basic major diameters up to and including 19
B568 Test Method for Measurement of Coating Thickness
mm because of the nonuniformity of thickness that can be
by X-Ray Spectrometry
expected on fine threads. However, a decision to use the
B571 Practice for Qualitative Adhesion Testing of Metallic
coating on such components may be made by the purchaser.
Coatings
1.3 This standard does not purport to address all of the
B602 Test Method for Attribute Sampling of Metallic and
safety concerns, if any, associated with its use. It is the
Inorganic Coatings
responsibility of the user of this standard to establish appro-
B634 Specification for Electrodeposited Coatings of
priate safety and health practices and determine the applica-
Rhodium for Engineering Use
bility of regulatory limitations prior to use.
B697 Guide for Selection of Sampling Plans for Inspection
2. Referenced Documents of Electrodeposited Metallic and Inorganic Coatings
B762 Test Method of Variables Sampling of Metallic and
2.1 ASTM Standards:
Inorganic Coatings
B183 Practice for Preparation of Low-Carbon Steel for
B765 Guide for Selection of Porosity and Gross Defect
Electroplating
Tests for Electrodeposits and Related Metallic Coatings
B242 Guide for Preparation of High-Carbon Steel for Elec-
B809 Test Method for Porosity in Metallic Coatings by
troplating
Humid Sulfur Vapor (“Flowers-of-Sulfur”)
B246 Specification for Tinned Hard-Drawn and Medium-
B849 Specification for Pre-Treatments of Iron or Steel for
Hard-Drawn Copper Wire for Electrical Purposes
Reducing Risk of Hydrogen Embrittlement
B252 Guide for Preparation of Zinc Alloy Die Castings for
B850 Guide for Post-Coating Treatments of Steel for Re-
Electroplating and Conversion Coatings
ducing the Risk of Hydrogen Embrittlement
B281 Practice for Preparation of Copper and Copper-Base
D3951 Practice for Commercial Packaging
Alloys for Electroplating and Conversion Coatings
B322 Guide for Cleaning Metals Prior to Electroplating
3. Terminology
3.1 Definitions:
This specification is under the jurisdiction of ASTM Committee B08 on
3.1.1 Many terms used in this standard are defined in
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
Terminology B374.
B08.08.04 on Soft Metals.
3.1.2 significant surface—that portion of a coated article’s
Current edition approved April 1, 2004. Published April 2004. Originally
approved in 1975. Last previous edition approved in 1999 as B605 – 95a (1999).
surface where the coating is required to meet all the require-
DOI: 10.1520/B0605-95AR04.
ments of the coating specification for that article. Significant
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
surfaces are those that are essential to the serviceability or
contact ASTM Customer Service at service@astm.org. 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.
B605 – 95a (2004)
TABLE 2 Tin-Nickel Coatings on Copper or Copper Alloys
function of the article, or which can be a source of corrosion
products or tarnish films that interfere with the function or Service Minimum
Thickness
Condition Thickness,
desirable appearance of the article. Significant surfaces are
Notation
Number µm
those surfaces that are identified by the purchaser by, for
A B B
5 Cu/Sn-Ni as specified as specified
example, indicating them on an engineering drawing of the
(above 45) (above 45)
A
product or marking a sample item of the product.
4 Cu/Sn-Ni 45 45
A
3 Cu/Sn-Ni 25 25
3.1.3 undercoating—a metallic coating layer between the
A
2 Cu/Sn-Ni 15 15
basis metal or substrate and the topmost metallic coating. The
A
0 Cu/Sn-Ni 44
thickness of an undercoating is usually greater than 0.8 µm.
A
An undercoating of copper 4.0 µm thick shall be applied on copper-zinc alloys
This is in contrast to strikes or flashes, whose thicknesses are
to serve as a zinc diffusion barrier.
B
Thickness of Sn-Ni shall be stated in a Thickness Notation. A statement of
generally lower.
Service Condition 5 is not sufficient.
4. Classifications
TABLE 3 Tin-Nickel Coatings on Zinc Alloys
4.1 Coating Grades—Six grades of coatings, designated by
Service Minimum
Thickness
service condition numbers, are covered by this specification.
Condition Thickness,
Notation
For each coating grade a coating thickness grade is specified Number µm
A
(see Tables 1-3).
4 Zn/Cu /Sn-Ni 45 45
A
4.2 Service Condition Number—The service condition 3 Zn/Cu /Sn-Ni 25 25
A
2 Zn/Cu /Sn-Ni 15 15
number indicates the severity of exposure for which the grade
A
1 Zn/Cu /Sn-Ni 8 8
of coating is intended.
A
An undercoating of copper 4.0 µm thick shall be applied to prevent zinc from
SC5—extended severe service
contaminating the Sn-Ni plating bath and to serve as a diffusion barrier.
SC4—very severe service
SC3—severe service
SC2—moderate service
5.1.5 Any requirement for submission of sample coated
SC1—mild service
articles (see 7.2.1),
SC0—mild service (copper and copper alloys only)
5.1.6 Whether or not location of rack marks is to be defined
NOTE 1—Typical service conditions for which the service condition
(see 7.2.1),
numbers are appropriate are given in Appendix X1.
5.1.7 Any requirement for porosity testing and the criteria
4.3 Coating Thickness Notation—The coating thickness is
for acceptance (see 7.5.2),
specified for each service condition in the following manner:
5.1.8 Heat treatment for stress relief, whether it has been
Basis metal/Undercoating (thickness)/Sn-Ni (thickness). For
performed by the purchaser, or is required (see 7.6),
example, Fe/Cu4/Sn-Ni25 would indicate a 25 µm tin-nickel
5.1.9 Heat treatment after electroplating, if required (see
coating over an iron or steel article with a 4-µm thick copper
7.7),
undercoating. All thickness notations are minimum thick-
5.1.10 Any packaging requirement (see section 7.8),
nesses.
5.1.11 Inspection procedure to be used (see Section 9),
5.1.12 Any requirement for certification (see Section 11),
5. Ordering Information
and
5.1 To make the application of this standard complete, the
5.1.13 Any requirement for test specimens (see 8.1.1).
purchaser needs to supply the following information to the
6. Material and Process
seller in the purchase order or other government documents.
5.1.1 The name, designation, and date of issue of this
6.1 Composition of Coating—Electrolytes that have been
standard,
investigated for producing Sn-Ni alloy deposits include cya-
5.1.2 Location of significant surface(s) (see section 3.1.2),
nide, fluoborate, pyrophosphate, and acetate, but the only one
5.1.3 The service number or coating thickness notation (see
in general commercial use is the fluoride-chloride formula-
4.2 and 4.3),
tion. Thedepositcontains35 6 5 %nickelwiththeremainder
5.1.4 Undercoating, if required (see 6.2 and Tables 1-3),
tin (see Note 2).
NOTE 2—The electrodeposited tin-nickel coating is a single-phase,
metastable compound, corresponding approximately to the formula SnNi.
TABLE 1 Tin-Nickel Coatings on Steel
It is stable at ordinary temperatures but starts to recrystallize at elevated
Service Minimum temperatures. The safe working temperature of the coating is 300°C,
Thickness
Condition Thickness,
although actual melting does not commence below 800°C. The coating is
Notation
Number µm
hard (700HV100). Like many such compounds, it is inherently somewhat
A B B
5 Fe/Cu /Sn-Ni as specified as specified brittle, but if it is free of internal stresses, the brittleness is not sufficient
(above 45) (above 45)
to impair its serviceability or to cause the coating to flake under impact.
A
4 Fe/Cu /Sn-Ni 45 45
Because of the brittleness of the tin-nickel, however, it is not possible to
A
3 Fe/Cu /Sn-Ni 25 25
fabricate parts by bending coated sheet material, because the compressive
2 Fe/Sn-Ni 15 15
stresses in the coating on the inside of the bend usually cause some of the
1 Fe/Sn-Ni 8 8
A
Copper undercoat shall be at least 4.0 µm.
B
Thickness of Sn-Ni shall be stated in a Thickness Notation. A statement of
Service Condition 5 is not sufficient. Lowenheim, F. A., Electroplating, McGraw-Hill Inc., 1978.
B605 – 95a (2004)
coating to flake off. To provide serviceability, the coating must be is less in interior corners and holes. Such surfaces are often exempt from
deposited in a stress-free condition. In addition, it is generally inadvisable thickness requirements. If the full thickness is required in those locations,
to specify tin-nickel finish for parts subject to deformation in service. the electroplater will have to use special techniques that will probably
raise the cost of the process.
6.2 Basis Metal—Tin-nickel can be deposited directly on
NOTE 7—The coating thickness requirement of this specification is a
steel, copper, and copper-base alloys. However, an undercoat-
minimum. Variation in the thickness from point to point on an article and
ing of copper can improve performance in some systems and from article to article in a production lot is inherent in electroplating.
Therefore, if all of the articles in a production are to meet the thickness
shall be used under the following conditions:
requirement, the average coating thickness for the production lot as a
6.2.1 On steel, a copper undercoating with a minimum
whole will be greater than the specified minimum.
thickness of 4 µm, shall be used for Service Conditions 3, 4,
7.4 Adhesion—The coatings shall be adherent to the basis
and 5.
metal when subject to either test, in accordance with 8.5.2 and
6.2.2 On copper-zinc alloys, a copper undercoating with a
8.5.3. There shall be no separation of the coating from the
minimum thickness of 4 µm shall be used for all service
substrate.
conditions to prevent diffusion of the zinc.
7.5 Integrity of the Coating:
6.2.3 Zinc-base alloys shall have an undercoating of a
7.5.1 Gross Defects/Mechanical Damage— The coatings
minimum of 4 µm of copper to prevent diffusion of the zinc
shall be free of mechanical damage, large pores, and similar
into the deposit and to prevent contamination of the electrolyte
gross defects. For some applications this requirement may be
with zinc.
relaxed to allow for a small number of such defects (per unit
NOTE 3—Tin-nickel-coated zinc-alloy diecastings shall never be re-
area), especially if they are outside the significant surfaces.
turned for remelting to prevent contamination of the zinc alloy with tin.
7.5.2 Porosity—Almostallas-platedelectrodepositscontain
some porosity. The amount of porosity that may be tolerable
7. Coating Requirements Coating Requirements
depends on the severity of the environment that the article is
7.1 Composition of Coating—The deposit shall contain
likely to encounter during service or storage. If the pores are
65 6 5 % tin, the balance nickel.
few in number or away from significant surfaces, their pres-
7.2 Appearance:
ence can often be tolerated. Such acceptance (or pass-fail)
7.2.1 The coating on all readily visible surfaces shall be
criteria shall be part of the product specification for the
smooth, fine grained, continuous, adherent, free of visible
particular article or coating requiring the porosity test (see 8.6
blisters, pits, nodules, indications of burning, excessive
for porosity test methods).
buildup, staining, and other defects. All tin-nickel coated
7.6 Pre-Treatments of Iron and Steel for Reducing the Risk
articles shall be clean and undamaged. When necessary,
of Hydrogen Embrittlement—Parts that are made of steels with
preliminary samples showing the finish shall be supplied for
ultimate tensile strengths of 1000 MPa (hardness of 31 HRC)
approval. Where a rack contact mark is unavoidable, its
or greater that have been machined, ground, cold formed, or
location shall be indicated on the article or its drawing.
cold straightened subsequent to heat treatment shall be heat
7.2.2 Defects and variations in appearance in the coating
treated prior to processing according to Specification B849.
that arise from surface conditions of the substrate (scratches,
The tensile strength shall be supplied by the purchaser.
pores, roll marks, inclusions, and the like) and that persist in
7.7 Post-Coating Treatments of Iron and Steel for Reducing
the coating despite the observance of good metal finishing
the Risk of Hydrogen Embrittlement—Parts that are made from
practices shall not be cause for rejection.
steels with ultimate tensile strengths equal to or greater than
NOTE 4—Coatings generally perform better in service when the sub-
1000 MPa (hardness of 31 HRC) and surface hardened parts
strate over which they are applied is smooth and free of torn metal,
shall require heat treatment according to Specification B850.
inclusions, pores, and other defects. The specifications covering the
7.8 Supplementary Requirements—Packaging—If packag-
unfinishedproductshouldprovidelimitsforthesedefects.Ametalfinisher
ing requirements are to be met under this Specification, they
can often remove defects through special treatments,
...
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