【国外标准】 Standard Specification for Coatings of Cadmium-Tin Mechanically Deposited

This specification covers the requirements for a coating that is a mixture of cadmium and tin mechanically deposited on metal products. The coating shall be 45 to 75 mass % cadmium, the remainder tin. All steel parts that have ultimate tensile strength of 1000 MPa and above and that contain tensile stresses caused by machining, grinding, straightening, or cold forming operation shall be given a stress relief heat treatment prior to cleaning and metal deposition. High-strength steels that have heavy oxide or scale shall be cleaned before application of the coating in accordance with guide B 242. Chromate treatment for Type II shall be done in a solution containing hexavalent chromium. The cadmium-tin coating shall be sufficiently adherent to the basis metal to pass the prescribed testing. Steel springs and other high-strength steel parts shall be free from hydrogen embrittlement. The coating shall be uniform in appearance and substantially free of blisters, pits, nodules, flaking and other defects that can adversely affect the function of the coating. Chemical composition of the cadmium-tin coating shall be determined when required on the purchase order by procedures given in methods E 87 or test methods E 396. The thickness of the coating shall be determined by the microscopical method, the magnetic method, or the beta backscatter method as applicable. Chromate conversion coatings of cadmium-tin both have an essentially silvery-white appearance. Adhesion of the cadmium-tin deposit to the basis metal shall be tested in a manner that is consistent with the service requirements of the coated article. Coated parts to be tested for the absence of embrittlement from cleaning shall be tested for brittle failure in accordance with a suitable method.1.1 This specification covers the requirements for a coating that is a mixture of cadmium and tin mechanically deposited on metal products. The coating is provided in various thicknesses up to and including 12 μm.1.2 Mechanical deposition greatly reduces the risk of hydrogen embrittlement and is suitable for coating bores and recesses in many parts that cannot be conveniently plated electrolytically. (See Appendix X1.)1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazards statements, see Section 7.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.