Reactive elements sulphur effect

Prokof ev [18] studied the effects of oligomeric polysulphides on the rate of sulphidation of copper foil in m-xylene. These oligomers contained linear polysulphide chains. It was reported that the polysulphides themselves did not sulphidise the copper at an appreciable rate. However, when used together with elemental sulphur, sulphidation occurred and the sulphide was more homogeneous and finer than by sulphur alone. These results were used to explain the more stable bonding to rubber containing polysulphides. Apparently, linear sulphides are not reactive but they insert sulphide and then become active for sulphidation. 

Once more, the presence of reactive elements allows protective oxide scales to form, even in the presence of sulphur. It is generally proposed that the reactive elements react with S and form sulphides, then stopping their detrimental effect on the oxide scale adherence [208,209]. However, very few studies were able to identify such compounds [210,211], even if S was detected [212], The role played by the RE then is preventing sulphur segregation at the oxide scale-metal interface [213]. 

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