METAL-ION AND EXOPOLYMER INTERACTION - A SURFACE ANALYTICAL STUDY

Various concentrations of molybdate (MoO42-) were added to the protein -containing and deproteinated exopolymers of the marine bacterium Dele ya marina. Interaction was investigated using x-ray photoelectron spec troscopy (XPS) and electron spin resonance (ESR). MoO42- reduction was observed exclusively in the deaerated protein-containing exopolymer, resulting in the formation of a Mo5+ species. This species appeared su sceptible to reoxidation in the presence of soluble oxygen. Only hexav alent molybdenum (Mo6+) was seen in the aerated suspension The reducin g agents may have been the residual proteins that remained in the exop olymer without subsequent deprotetnation. The influence of this reduct ion on corrosion resistance of Mo-bearing stainless steels (SS) was si mulated with an austenitic type 304 SS (UNS S30400), whose surface was treated with MoO42- before exposure to the exopolymer. In addition to formation of the Mo5+ species, a small amount of molybdenum dioxide ( MoO2) was detected, and hydration of the passive film increased No evi dence was found to indicate the exopolymer attachment compromised corr osion resistance of the SS In deaerated 0.1 M hydrochloric acid (HCl).