Investigation of the local structure around iron dispersed in vinyl chloride–vinylidene chloride (VC–VdC) copolymer coatings on mild steel using glancing-angle X-ray absorption spectroscopy

Abstract

The chemistry occurring in vinyl chloride–vinylidene chloride polymer coatings on mild steel has been investigated by probing the local environment around Fe ions using glancing-angle X-ray absorption spectroscopy. Measurements made as a function of penetration depth reveal that close to the air interface the Fe species are present as octahedrally co-ordinated Fe^III and have a local structure similar to that observed in disordered γ-FeOOH. Although this structure is found to be independent of the pH of the coating formulation, Fe ion transport from the metal substrate is apparently enhanced at acidic pH formulations. Deeper into the coating the Fe has a structure typical of a mixed tetrahedral–octahedral environment such as Fe₃O₄.