ASTM B605-95a(1999)
(Specification)Standard Specification for Electrodeposited Coatings of Tin-Nickel Alloy
Standard Specification for Electrodeposited Coatings of Tin-Nickel Alloy
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: B 605 – 95a (Reapproved 1999)
Standard Specification for
Electrodeposited Coatings of Tin-Nickel Alloy
This standard is issued under the fixed designation B 605; 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 Coating Thicknesses by Microscopical Examination of a
Cross Section
1.1 This specification covers the requirements for electrode-
B 499 Test Method for Measurement of Coating Thick-
posited tin-nickel alloy coatings from aqueous solutions in-
nesses by the Magnetic Method: Nonmagnetic Coatings on
tended for the corrosion protection of fabricated articles of
Magnetic Basis Metals
iron, steel, zinc-base alloys, copper, and copper alloys. The
B 504 Test Method for Measurement of Thickness of Me-
composition of the alloy remains constant at 65/35 tin-nickel in
tallic Coatings by the Coulometric Method
spite of wide fluctuations in both composition and operating
B 507 Practice for Design of Articles to Be Electroplated on
conditions. The composition corresponds quite closely to an
Racks
equiatomic ratio, and the process favors the co-deposition of
B 567 Test Method for Measurement of Coating Thickness
tin and nickel atoms at identical rates.
by the Beta Backscatter Method
1.2 This specification does not apply to sheet, strip, or wire
B 568 Test Method for Measurement of Coating Thickness
in the fabricated form. It also may not be applicable to threaded
by X-Ray Spectrometry
articles having basic major diameters up to and including 19
B 571 Test Methods for Adhesion of Metallic Coatings
mm because of the nonuniformity of thickness that can be
B 602 Test Method for Attribute Sampling of Metallic and
expected on fine threads. However, a decision to use the
Inorganic Coatings
coating on such components may be made by the purchaser.
B 634 Specification for Electrodeposited Coatings of
1.3 This standard does not purport to address all of the
Rhodium for Engineering Use
safety concerns, if any, associated with its use. It is the
B 697 Guide for Selection of Sampling Plans for Inspection
responsibility of the user of this standard to establish appro-
of Electrodeposited Metallic and Inorganic Coatings
priate safety and health practices and determine the applica-
B 762 Method of Variables Sampling of Metallic and Inor-
bility of regulatory limitations prior to use.
ganic Coatings
2. Referenced Documents
B 765 Guide for Selection of Porosity Tests for Electrode-
posits and Related Metallic Coatings
2.1 ASTM Standards:
B 809 Test Method for Porosity in Metallic Coatings by
B 183 Practice for Preparation of Low-Carbon Steel for
Humid Sulfur Vapor (Flowers of Sulfur)
Electroplating
B 849 Specification for Pre-Treatments of Iron or Steel for
B 242 Practice for Preparation of High-Carbon Steel for
Reducing the Risk of Hydrogen Embrittlement
Electroplating
B 850 Specification for Post-Coating Treatments of Iron or
B 246 Specification for Tinned Hard-Drawn and Medium-
Steel for Reducing the Risk of Hydrogen Embrittlement
Hard-Drawn Copper Wire for Electrical Purposes
D 3951 Practice for Commercial Packaging
B 252 Guide for Preparation of Zinc Alloy Die Castings for
Electroplating and Conversion Coatings
3. Terminology
B 281 Practice for Preparation of Copper and Copper-Base
2 3.1 Definitions:
Alloys for Electroplating and Conversion Coatings
3.1.1 Many terms used in this standard are defined in
B 322 Practice for Cleaning Metals Prior to Electroplating
Terminology B 374.
B 374 Terminology Relating to Electroplating
3.1.2 significant surface—that portion of a coated article’s
B 487 Test Method for Measurement of Metal and Oxide
surface where the coating is required to meet all the require-
ments of the coating specification for that article. Significant
1 surfaces are those that are essential to the serviceability or
This specification is under the jurisdiction of ASTM Committee B-8 on
Metallic and Inorganic Coatingsand is the direct responsibility of Subcommittee function of the article, or which can be a source of corrosion
B08.08.04 on Light Metals.
products or tarnish films that interfere with the function or
Current edition approved July 15, 1995. Published September 1995. Originally
published as B 605 – 75. Last previous edition B 605 – 95.
Annual Book of ASTM Standards, Vol 02.05.
3 4
Annual Book of ASTM Standards, Vol 02.03. 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 605
TABLE 2 Tin-Nickel Coatings on Copper or Copper Alloys
desirable appearance of the article. Significant surfaces are
those surfaces that are identified by the purchaser by, for Service Minimum
Thickness
Condition Thickness,
example, indicating them on an engineering drawing of the
Notation
Number μm
product or marking a sample item of the product.
A B B
5 Cu/Sn-Ni as specified as specified
3.1.3 undercoating—a metallic coating layer between the
(above 45) (above 45)
A
basis metal or substrate and the topmost metallic coating. The
4 Cu/Sn-Ni 45 45
A
3 Cu/Sn-Ni 25 25
thickness of an undercoating is usually greater than 0.8 μm.
A
2 Cu/Sn-Ni 15 15
This is in contrast to strikes or flashes, whose thicknesses are
A
0 Cu/Sn-Ni 44
generally lower.
A
An undercoating of copper 4.0 μm thick shall be applied on copper-zinc alloys
to serve as a zinc diffusion barrier.
B
Thickness of Sn-Ni shall be stated in a Thickness Notation. A statement of
4. Classifications
Service Condition 5 is not sufficient.
4.1 Coating Grades—Six grades of coatings, designated by
service condition numbers, are covered by this specification.
5.1.6 Whether or not location of rack marks is to be defined
For each coating grade a coating thickness grade is specified
(see 7.2.1),
(see Tables 1-3).
5.1.7 Any requirement for porosity testing and the criteria
4.2 Service Condition Number—The service condition
for acceptance (see 7.5.2),
number indicates the severity of exposure for which the grade
5.1.8 Heat treatment for stress relief, whether it has been
of coating is intended.
performed by the purchaser, or is required (see 7.6),
SC5—extended severe service
5.1.9 Heat treatment after electroplating, if required (see
SC4—very severe service
SC3—severe service
7.7),
SC2—moderate service
5.1.10 Any packaging requirement (see section 7.8),
SC1—mild service
SC0—mild service (copper and copper alloys only) 5.1.11 Inspection procedure to be used (see Section 9),
5.1.12 Any requirement for certification (see Section 11),
NOTE 1—Typical service conditions for which the service condition
and
numbers are appropriate are given in Appendix X1.
5.1.13 Any requirement for test specimens (see 8.1.1).
4.3 Coating Thickness Notation—The coating thickness is
specified for each service condition in the following manner:
TABLE 3 Tin-Nickel Coatings on Zinc Alloys
Basis metal/Undercoating (thickness)/Sn-Ni (thickness). For
Service Minimum
example, Fe/Cu4/Sn-Ni25 would indicate a 25 μm tin-nickel
Thickness
Condition Thickness,
coating over an iron or steel article with a 4-μm thick copper
Notation
Number μm
undercoating. All thickness notations are minimum thick-
A
4 Zn/Cu /Sn-Ni 45 45
nesses.
A
3 Zn/Cu /Sn-Ni 25 25
A
2 Zn/Cu /Sn-Ni 15 15
A
1 Zn/Cu /Sn-Ni 8 8
5. Ordering Information
A
An undercoating of copper 4.0 μm thick shall be applied to prevent zinc from
5.1 To make the application of this standard complete, the
contaminating the Sn-Ni plating bath and to serve as a diffusion barrier.
purchaser needs to supply the following information to the
seller in the purchase order or other government documents.
6. Material and Process
5.1.1 The name, designation, and date of issue of this
standard,
6.1 Composition of Coating—Electrolytes that have been
5.1.2 Location of significant surface(s) (see section 3.1.2),
investigated for producing Sn-Ni alloy deposits include cya-
5.1.3 The service number or coating thickness notation (see
nide, fluoborate, pyrophosphate, and acetate, but the only one
4.2 and 4.3),
in general commercial use is the fluoride-chloride formula-
5.1.4 Undercoating, if required (see 6.2 and Tables 1-3),
tion. The deposit contains 35 6 5 % nickel with the remainder
5.1.5 Any requirement for submission of sample coated
tin (see Note 2).
articles (see 7.2.1),
NOTE 2—The electrodeposited tin-nickel coating is a single-phase,
metastable compound, corresponding approximately to the formula SnNi.
It is stable at ordinary temperatures but starts to recrystallize at elevated
TABLE 1 Tin-Nickel Coatings on Steel
temperatures. The safe working temperature of the coating is 300°C,
although actual melting does not commence below 800°C. The coating is
Service Minimum
Thickness
Condition Thickness, hard (700HV100). Like many such compounds, it is inherently somewhat
Notation
Number μm
brittle, but if it is free of internal stresses, the brittleness is not sufficient
A B B
to impair its serviceability or to cause the coating to flake under impact.
5 Fe/Cu /Sn-Ni as specified as specified
(above 45) (above 45) Because of the brittleness of the tin-nickel, however, it is not possible to
A
4 Fe/Cu /Sn-Ni 45 45
fabricate parts by bending coated sheet material, because the compressive
A
3 Fe/Cu /Sn-Ni 25 25
stresses in the coating on the inside of the bend usually cause some of the
2 Fe/Sn-Ni 15 15
coating to flake off. To provide serviceability, the coating must be
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.
B 605
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.
shall be used under the following conditions: Therefore, if all of the articles in a production are to meet the thickness
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,
and 5.
7.4 Adhesion—The coatings shall be adherent to the basis
6.2.2 On copper-zinc alloys, a copper undercoating with a
metal when subject to either test, in accordance with 8.5.2 and
minimum thickness of 4 μm shall be used for all service
8.5.3. There shall be no separation of the coating from the
conditions to prevent diffusion of the zinc.
substrate.
6.2.3 Zinc-base alloys shall have an undercoating of a
7.5 Integrity of the Coating:
minimum of 4 μm of copper to prevent diffusion of the zinc
7.5.1 Gross Defects/Mechanical Damage— The coatings
into the deposit and to prevent contamination of the electrolyte
shall be free of mechanical damage, large pores, and similar
with zinc.
gross defects. For some applications this requirement may be
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—Almost all as-plated electrodeposits contain
7. Coating Requirements some porosity. The amount of porosity that may be tolerable
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 B 849.
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 B 850.
inclusions, pores, and other defects. The specifications covering the
7.8 Supplementary Requirements—Packaging—If packag-
unfinished product should provide limits for these defects. A metal finisher
ing requirements are to be met under this Specification, they
can often remove defects through special treatments, such as grinding,
polishing, abrasive blasting, chemical etches, and electropolishing. How- shall be in accordance with Practice D 3951.
ever, these are not normal
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