Coatings of Cadmium Mechanically Deposited
AASHTO Designation: M 299-05
ASTM Designation:B 696-00 (2004t1
1.1This specification covers the requirements for a coating of cadmium 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 hy• drogen embrittlement and is suitable for coating bores and recesses in many parts that cannot be
conveniently electro• plated (sec Appendix X3).
1.3 Cadmium coatings are usually applied to provide engi• neering propenies and corrosion resistance.
The performance of a cadmium coating depends largely on its thickness and the kind of environment to which it is exposed.
Without proof of satisfactory correlation, accelerated tests such as the salt spray (fog) test cannot be relied upon to predict performance in other environments, nor will these serve as comparative measures of the corrosion resistance afforded by coatings of different metals.
Thus, although there is a marked superiority of cad• mium coatings over zinc coatings of equal thickness in the salt spray test, this is often not the case under
conditions of use, so that further testing in the service environment should be conducted. ·
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