Parts are rack or barrel plated to ASTM B standard thicknesses from ” to “, depending on the base metal and application. Pure % tin is. Designation: B – 97 (Reapproved )e1 Standard Speci?cation for Electrodeposited Coatings of Tin1 This standard is issued under the. ASTM B Standard Specification for Electrodeposited Coatings of Tin.
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Blackening at pores will be evidence of porosity.
A bright coating completely covering the signi? When necessary, preliminary samples showing the? ASTM does not give asmt warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.
Evidence of diffusion is the formation of a layer of copper-tin intermetallic at the interface and diffusion of zinc to the surface if the substrate is brass. Coatings shall be grouped into six service classes, which is based on the minimum thickness and severity of service required for the coating, and three surface appearance types, which is based on the type electroplating process employed. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every?
In many applications for axtm coatings, whisker growth has not been a problem, but there are critical applications X6. The test must yield a numerical value, and certain statistical requirements must be met. The surface appearance types are matte tin electrodeposits, bright tin electrodeposits, and flow-brightened electrodeposits. Coatings shall be sampled, tested and conform accordingly to specified requirements as to appearance, purity, local and mean thickness, integrity including gross defects, mechanical damage, and porosityadhesion, solderability, and hydrogen embrittlement relief.
Porosity increases as the coating thickness decreases, so that minimum thicknesses must be specified for each application. Also see Note 5.
Practically all of the following methods take into account the chief cause of tin whiskering, which is the presence of stresses in the tin coating 8: The diffusion is slow at room temperature and rapid at elevated temperatures. However, some of asrm platings cannot be used in contact with food. Moderate exposure conditions, usually indoors, but more severe than Class B. Very severe service conditions, including elevated temperatures, where underlying metal diffusion and intermetallic formation processes are accelerated.
A thicker coating b54 nickel may be required in some situations for additional retardation. There needs to be sufficient free tin below the oxide layer in order for this to occur, because the intermetallic compounds formed from tin and the basis metal will not react in this way 7. Also found on baking pans after re?
Poor adhesion will be shown if the coating blisters, cracks, or peels. Remove asttm articles, rinse them in clean water, wipe and brush as necessary v545 remove smut antimony residuesand dry. The maximum thickness for? This specification does not cover hot-dipped tin or other non-electrodeposited coatings, and mill products.
Tin coatings are used to provide a low contactresistance surface, to protect against corrosion see 1. The thickness is less in interior corners and holes.
Dry and weigh with an accuracy of at least 1 part in Visual examination, time of wetting, measurement of area of spread, and calculation of spread values are used to assess solderability 1, 2. The goal is to de? If the quality of the deposit is also poor, the blister may crack, and the plating will peel away from the basis metal. When Test Method B is used to measure these types of coatings, the measuring instrument shall be calibrated with thickness standards that have the same substrate and same composition of coating as the product.
This abstract is a brief summary of the referenced standard. Addition of the sulfuric acid may be made before the test specimens are placed in position, provided that the cabinet is closed within 5 min of addition of the acid.
B — 97 Reapproved e1 Standard Speci? Class A Minimum Thickness 2.
NOTE 4—Thickness of electrodeposited coatings varies from point to g545 on the surfaces of a product see Practice B Poor adhesion will be shown by the appearance of a loose blister that grows as rubbing is continued. Black spots or lines are evidence of mechanical damage or gross defects. Practice B may be consulted to determine the most appropriate test method. The shape of the part is also a factor;?
It gradually thickens, and it may eventually produce a dull gray appearance. 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.
Diffusion may lead to darkening of a thin coating and impairment of its solderability characteristics, particularly after long storage. Parts coated satm tin can be assembled safely in contact with iron and steel, tin-coated aluminum, yellow chromated zinc, cadmium, and solder coatings. This specification covers the requirements for electrodeposited tin coatings applied to metallic articles to provide a low contact resistance surface, to protect against corrosion, to facilitate soldering, to provide anti-galling properties, and to be a stop-off coating in the nitriding of high-strength steels.
If they do not, Test Method B identi? Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.