ASTM B545-13(R2021) pdf free download

ASTM B545-13(R2021) pdf free download.Standard Specification for Electrodeposited Coatings of Tin
1. Scope
1.1 This specification covers the requirements for electrode- posited (electroplated) coatings of tin applied to metallic articles. Tin coatings are used to provide a low contact- resistance surface, to protect against corrosion (see 1.2), to facilitate soldering, to provide anti-galling properties, and to be a stopoff coating in the nitriding of high-strength steels. 1.2 Some corrosion can be expected from tin coatings exposed outdoors. In normal indoor exposure, tin is protective on iron, steel, nickel, copper, and their alloys. Corrosion can be expected at discontinuities in the coating (such as pores) due to galvanic couples formed between the tin and the underlying metal through the discontinuities, especially in humid atmo- spheres. Porosity increases as the coating thickness decreases, so that minimum thicknesses must be specified for each application. Parts coated with tin can be assembled safely in contact with iron and steel, tin-coated aluminum, yellow chromated zinc, cadmium, and solder coatings. (See X5.1 for oxidation and corrosion properties.) 1.3 This specification applies to electroplated coatings of not less than 99 % tin (except where deliberately alloyed for special purposes, as stated in X6.3) obtained from any of the available tin electroplating processes (see 4.3). 1.4 This specification does not apply to hot-dipped tin or other non-electrodeposited coating; it also does not apply to mill products. For mill products, refer to Specifications A623 or A623M. 1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.6 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 appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use.
6. Coating Requirements
6.1 Substrate—The metal substrate shall be subjected to such surface preparation, cleaning, and electroplating proce- dures as are necessary to yield deposits with the desired quality. N OTE 2—Careful preparation of metal surfaces is necessary in order to assure good adhesion and quality. For suitable methods, see Practices B183, B242, B281, B320, B322, and B558. Also see 6.6. 6.2 Electroplating shall be applied after all basis metal heat treatments and mechanical operations have been completed. 6.3 Appearance—Tin coatings shall have the characteristic appearance, including surface texture (4.3), for the process used. The appearance shall be uniform throughout, insofar as the basis metal will permit. They shall be adherent and visually free ofblisters, pits, peeled areas, cracks, nodules, and unplated areas. They shall not be stained or discolored. Flow-brightened coatings shall be free of dewetted areas and beads. All surfaces shall be substantially free of grease or oil used in the flow-brightening process. 6.4 All tin-coated articles shall be clean and undamaged. When necessary, preliminary samples showing the finish shall be supplied to and approved by the purchaser. Where a contact mark is inevitable, its location shall be subject to agreement between the supplier and the purchaser. 6.5 Thickness of Coatings—Tin coatings on articles shall conform to the thickness requirements specified in 4.2 as to the minimum thickness on significant surfaces. 6.5.1 Local Thickness—The thickness values specified in 4.2 are the minimum local thicknesses measured by one or more of the methods given in Practice B659 at any number of desired spots on the significant surface. 6.5.2 Mean Thickness—When specified by the purchaser, instead of being a local minimum requirement, the thickness requirement can be a minimum (arithmetic) mean thickness.N OTE 3—Specification of the coating thickness in terms of the mean is normally made when the coated articles are small and relatively simple, such as connector pins and terminals. N OTE 4—Thickness of electrodeposited coatings varies from point to point on the surfaces of a product (see Practice B507). The thickness is less in interior corners and holes. Such surfaces are normally exempt from the thickness requirement. If the full thickness is required on these surfaces, the electroplater will have to use special techniques that probably will increase the cost of the process. N OTE 5—When articles are plated by mass plating techniques (such as barrel plating), such measurement methods as “strip and weigh” or “weigh before and after plating” may be used to determine the mean thickness.