Influence of Residual Rust on Underlying Steel Surface on Performance of Heavy-duty Coating

The influence of the residual rust on the steel surface before applying a heavy-duty coating on the performance was investigated under two accelerated corrosion tests; sunshine weathering meter and immersion tests. The different amounts of the rust were formed on the steel sheets by immersing in NaCl solution for various time periods. They were dried and painted with Polyester-urethane resin of 260 μm thick. The coating degradation and underlying steel corrosion were evaluated by surface observation and electrochemical impedance spectroscopy (EIS). The feasibility of the application of EIS to evaluation of the corrosion performance of the heavy-duty paint was also discussed.