The Application of Electroanalytical Techniques to the Study of Coating Systems

Abstract

Electroanalytical techniques are often employed to augment standard practices utilized to study and characterize coating performance on metal substrates, yielding information that is not provided by standard coating analysis methods. Electrochemical impedance spectroscopy (EIS) was utilized to study epoxy-amine coatings incorporating oligomers and monomers of phenylenediamine in the coating structure; these results were compared to unusual EIS results obtained in previous studies of organic-inorganic hybrid sol-gel coatings attributed to the sol-gel structure. With a different coating structure, the unusual results were replicated in coatings containing phenylenediamine oligomers but not monomer. The results suggested the oligomers caused the coatings to act as osmotic membranes. Potentiodynamic polarization studies were utilized to study a highly alkaline chemical bath used for the deposition of magnetite on steel. The results were used to develop a working model of how the bath functions and explain the high temperature and pH required for proper bath function.