Thermodynamic evaluation of the copper-rich part of the CuHOSP system at low temperatures

Calculations for OFP-copper give copper sulphide and copper phosphate as stable phases. No stable hydrogen-rich compound is found stable at atmospheric pressures. Calculations for oxygen-free copper (OF-copper) gives copper oxide instead of copper phosphate. This copper oxide has a lower stability than the copper phosphate, and the copper oxide is more easily reduced by hydrogen forming water vapour. This makes phosphorus an important alloying element for copper alloys in order to minimise the risk of hydrogen embrittlement in copper.