B, Si, As, Sn, Sb, Pb, Bi
As is known from the classical example of solder, the melting point of the mixture of tin and lead (183°C) is lower than that of the pure metals tin (232°C) and lead (327°C). This effect of the reduction in melting point also occurs when platinum metals come into contact with these elements.
Phosphorus is one of the classical “platinum poisons” with one of the lowest eutectic temperatures. With phosphorus in the form of phosphates, on the other hand, catastrophic corrosion does not occur. This can, however, lead to an increase in the surface roughness and to mechanical embrittlement.
Whereas sulfur in the form of sulfates is relatively harmless, sulfides can cause substantial embrittlement of the platinum components.
Further Elements and Compounds
Besides its influence in reducing oxides of the “platinum poisons”, carbon can diffuse into the grain boundaries and can cause a separation of the grain boundaries, leading to porosity.
Carbides and silicides
Contact with silicon carbide (e.g., SiC-insulating ceramic), or with molybdenum disilicide (MoSi2-heating elements) leads to immediate melting of the material and thus to the failure of the component.