Performance of Polyurea Coating Under Water Immersion at High Temperature

Coating is a common method used to prevent corrosion. This method is widely used in industry as it is most economical. However, some coatings fail at extreme condition such as in the internal section of deaerator which operates at high temperature in water immersion. This project was conducted to evaluate the performance of new coating system which is polyurea to be applied under this condition. Water immersion test was conducted in accordance to ASTM D870 where the carbon steel coated specimens with four different dry film thickness (DFT) were immersed in tap water at 65ºC for 42 days. This test results in rusting, softening and change of colour of the coating. Besides that, an Electrochemical Impedance Spectroscopy (EIS) was carried out to determine the corrosion rate of polyurea coating. A 2.00mm polyurea coated specimen and uncoated carbon steel were immersed in tap water at 65oC for 7 days. This test shows that polyurea coated specimen have lower corrosion rate. The objectives of this project were achieved. From these two tests, polyurea coating can be a suitable candidate to protect internal section of deaerator which operates under water immersion at high temperature provided a proper surface preparation, coating application and zero initial coating defects are necessary for this coating to have excellent performance and avoid coating failure.