Cadmium plating specifications

Attack on metals can be a function of fuel components as well as of water and oxygen. Organic acids react with cadmium plating and 2inc coatings. Traces of H2S and free sulfur react with silver used in older piston pumps and with copper used in bearings and brass fittings. Specification limits by copper and silver strip corrosion tests are requited for fuels to forestall these reactions. 

The future of cadmium plating is in question because of cadmium toxicity (83). Cyanide-free cadmium plating systems have experienced some growth. Acid cadmium, based on cadmium sulfate compositions, is replacing some cyanide baths in the United States. The fluoborate cadmium is reported in use in the UK, especially in barrel plating (84). Cadmium plating is covered by ASTM (85), U.S. government, and ISO specifications (86). 

Cadmium plating for general engineering use is covered by BS 1706 1960 and BS 3382 1961, and for aircraft parts by Ministry of Aviation Supply Specification DTD 904. Special requirements for very strong steels are given in Defence Standard 03-4 (Directorate of Standardisation, Ministry of Defence). 

A bolt from an aircraft flap control unit fractured in the threaded region of the shank near the shoulder with the head upon installation after a major service. The bolt was made from cadmium-plated high-strength steel. The bolt conformed to the specifications and had ultimate tensile strength of 4400 MPa. 

Electroplated layers that incorporate other materials to give specific surface properties represent a stimulating field of development. A major example has arisen from the desire to replace cadmium plating of nuts and bolts most existing coatings are unsuitable because they do not have the antigalling properties (i.e., low coefficient of friction) of cadmium. Co-deposition of zinc and finely divided colloidal graphite is a possible alternative. 

For those who wish to apply a full etch procedure to zinc coated or cadmium plated metal, McIntyre (1972) gives appendices with very full specification details in his paper on bonding to cadmiiun and zinc. 

The structural and electrochemical characteristics of cadmium electrodes with nickel introduced in metallic state into the active material of the electrode by electroless plating were studied [213]. The specific role played by hetero phase interactions between nickel and cadmium in the mechanism of the Cd electrode activation was substantiated experimentally. 

Nickel oxide electrodes constitute the positive plates of several storage systems (among which nickel-zinc, nickel cadmium, nickel metal-hydride, sodium-nickel chloride) [16]. In recent years, the high-specific energy and specific power of Ni-Zn systems has increased the interest in their use for electric vehicles with respect to the past years, when their application was essentially limited by a short cycle life. 

QQ-P-416, Federal Specification Plating Cadmium (Electrodeposited), IBR approved for 1926.104(e). 

---