Corrosion Life Prediction of Organic Coating by Gray Model Based on Low-frequency Imdepance Modulus

When an organic coating is exposed to a corrosive environment for a long period, the combined effects of various factors would result in a gradual declination of the anti-corrosion performance. Therefore, the service life of organic coatings is shortened and the protective effects on the substrate is weakened. However, the coating corrosion process can't be exhibited well by traditional performance parameters. The electrochemical impedance spectroscopy (EIS) can be applied to coating impedance analysis, and represents the failure process of the coating. To predict the life of organic coating in the corrosive environment, this paper utilizes the gray theory model and the exponential model for fitting the low-frequency impedance module value. The results indicate that the gray theory model has a better fitting effect than the conventional exponential model. Meanwhile, the gap between predictions and threshold gets narrow when the experimental data is gradually closed to the organic coating life. Thus, the gray theory model is recommended to predict the life of the organic coating.