Study on corrosion protection of organic coatings using electrochemical techniques: Thermal property characterization, film thickness investigation, and coating performance evaluation.

摘要

As an initial effort to establish a rapid, accurate, and comprehensive testing protocol for performance evaluation and lifetime prediction of corrosion protective coatings, the effects of coating thermal characteristics, coating application parameters, and coating formulation variations on corrosion protection have been explored. The study has been accomplished primarily through modern electrochemical techniques, such as Electrochemical Noise Methods (ENM) and Electrochemical Impedance Spectroscopy (EIS), with the aid of traditional thermal analysis, surface characterization, and appearance inspection. The employed electrochemical techniques have exhibited usefulness as powerful testing tools that have provided valuable results in good agreement with field observations and other measures by traditional methods.; Thermal property characterization on fusion bonded epoxy (FBE) pipeline coatings has shown that coating electrical resistances decreased as temperature rose with a distinct thermal transition point corresponding to glass transition temperature (T_g) of the immersed coatings. The change in coating capacitance with temperature revealed the irreversible process of water ingress and the effects of electrolyte plasticization in the coating films.; Film thickness investigation on marine coating systems has demonstrated that film thickness has significant influences on coating corrosion protection. Better performance is expected for a coating system with thicker film thickness as well as with more coating layers when applied at a constant film thickness. The results indicate that there was a possible critical minimum film thickness above which coating protective performance was greatly enhanced and that there was also a maximum limiting film thickness above which increasing film thickness made little contribution to corrosion protection.; Coating performance evaluation on aircraft coating systems has offered accurate performance ranking and reasonable lifetime prediction for high-quality, anticorrosive coatings. The mechanisms of corrosion protection by several coating systems with various types of polymers and pigment volume concentrations (PVC) have been discovered.; Future work will consider a broader selection of materials, different test conditions, and a greater variety of characterization techniques. More sophisticated data analysis methods also need to be developed.