Effects of Temperature and Glass Transition on the Performance of Polymer Coatings on Steels

The effects of temperature and glass transition on the corrosion protection behavior of an epoxy/urethane polymer coating on steels was investigated. The polymer experience glass transition at 67 ± 1 °C when heating at 4 °C/min. The ohmic resistance of the coating decreased by 4 orders of magnitude and the coating capacitance increased by about 2 times when the temperature increased from 20 to 80 °C. The ohmic resistance and capacitance of the coatings changed correspondingly to heating and cooling cycles, but the process is not totally reversible. The effect of temperature on the ohmic resistance of the coatings is attributed to the change in the size, the tortousity, and the number of the continuous pores in the coating. The effect of glass transition on the corrosion protection behavior of the coatings during a short period of exposure to a heat source was insignicant.