Evaluation of corrosion behavior of ion vapor deposited aluminum related coating systems

Experiments were conducted to investigate the effectiveness of ion vapor deposited (IVD) aluminum as a base coat for polyurethane topcoat systems in marine environments. Three test environments were used including marine atmospheric atmosphere, quiescent filtered seawater open to laboratory air and aerated seawater. Visual observation and electrochemical impedance spectroscopy techniques were primary testing methods; other characterizations included adhesion tape test, coating thickness measurements, holiday detection, optical microscopy, open circuit potential measurements and potentiodynamic polarization. It was found that IVD aluminum was a good candidate for replacement of environmentally sensitive coatings on AA2219-T87 and AISI 4340 steel substrates, respectively. The IVD aluminum coating provided good sacrificial protection and served as a good base for polyurethane topcoat systems. Electrochemical impedance spectroscopy was a suitable method to predict coating performance in the early stages of exposure.