Bolts cadmium-plated

Some cadmium-plated bolts and nuts were purchased and installed as a test in the plant. More bolts were purchased and eventually some of the cadmium-plated bolts were installed on the outlet piping flanges of a cracking furnace. The high temperature outlet flanges on the furnace started to weep a bit. An experienced, intelligent pipefitter attempted to snug up a few bolts and the nuts crumbled. (The cause of the failure was later determined to be due to corrosion phenomena called liquid metal embrittlement. )... 

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. 

The embrittlement is attributed to cadmium plating (21) on the bolts applied to protect them from corrosion. During cadmium plating, hydrogen is absorbed by steel, and cadmium acts as a barrier for the escape of hydrogen. In high-strength steels... 

Although cadmium has the nearest potential to that of aluminum in many environments, and cadmium-plated steel screws, bolts, trim, and so on, can be used in... 

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. 

Various bolt/nut combinations have been used with modular seals, ranging from vanilla cadmium-plated carbon steel to today s more exotic metric two-part zinc dichromate sub-coatings per ASTM B-663 under a propriety organic outer coating for superior corrosion resistance. To benchmark the corrosion resistance of these different combinations, four bolts were continuously immersed in tap water for four years, the results of which are shown in Figure 5. 

Cadmium plated bolts - the cadmium vaporizes easily and should be stripped before the bolts are used. Note Cadmium plating can be stripped by a short immersion at room temperature in a solution of concentrated HCl (2 liters) + Sb203 (30g) + DI water (500 ml). 

To complete the assembly of a cell, the interleaved electrode groups are bolted to a cov er and the cover is sealed to a container. Originally, nickel-plated steel was the predominant material for cell containers but, more recently plastic containers have been used for a considerable proportion of pocket nickel-cadmium cells. Polyethylene, high impact polystyrene, and a copolymer of propylene and ethylene have been the most widely used plastics. 

Steel hardware, including nuts and bolts, is often coated with a thin plating of cadmium. Explain the function of the cadmium layer. 

ELV stands for End of Life Vehicle and the directive to control the use of some hazardous substances mainly for automobiles. Lead, mercury, cadmium, and hexavalent chromium were the main targets for this directive. Particularly, the impact of controlling hexavalent chromium was very strong in plating industries, since a lot of hexavalent chromium was used for the surface finishing of automobiles. Conventionally, bolts and nuts used for automobiles were surface finished by chromate conversion coating. 

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