Copaslip (presumably similar to Permatex Copper Anti-seize lubricant )
Or when a compound containing metallic copper is not acceptable PBC (PolyButylCuprysil)
Never actually come across it but there is another alternative to Copaslip from the same manufacturers, namely Alumslip for use "where there is a prejudice against the presence of copper" ( similar to Permatex Anti-seize lubricant ??)
