EFFECT OF TRACE AMOUNTS OF FE ON SULPHIDING OF CU BY H2S

The rate at which Cu sulphides form on Cu in 1%H2S-dry air is increased by vacuum annealing which apparently concentrates the Fe impurities at grain boundaries. Still faster rates are observed when amounts of Fe equivalent to a fractional monolayer are deposited on a polished Cu surface, producing a maximum rate at 100ng Fe/cm2. Larger amounts of Fe result in the sulphiding rate decreasing from the maximum. Changes in surface potential when CO is adsorbed provide evidence that the iron is present as crystallites; beyond the maximum the crystallites are sufficiently large to block active sites on the Cu surface for S incorporation. © 1968 Pergamon Press.