The Study On Cathodic Performance Of Epoxy Coatings With Different Components In Seawater

In this paper,the cathodic stripping test,electrochemical test method and modern physical testing technique were used to detect the cathodic stripping and corrosion resistance of 16 kinds of epoxy coatings in seawater,and then the gray system theoretical model was used to study the coating life.And to provide experimental basis for the development of new corrosion-resistant,cathode-resistant epoxy coating.The cathodic stripping radius and cathodic protection current in seawater at different time and at different temperature were tested by cathodic stripping test.The results showed that the failure rate of the coating under 65℃ constant voltage of 28℃In the seawater,the failure rate is faster under constant potential impregnation at -3.5V for 24 h and at -1.5V for 48 h in 65℃ seawater,and the porosity increases with the constant potential of-1.5V at 25℃ in seawater for 28d,The resistance of the coating decreases and the capacitance increases,thus accelerating the seawater solution in the coating penetration rate.The open circuit potential and AC impedance of epoxy coatings in seawater were analyzed by electrochemical test.It was found that the AC impedance of 16 epoxy coatings decreased with the increase of immersion time.Which is still close to or greater than 10~8 Ω·cm~2,indicating that the coating still presents a high resistance,low capacitance of the effective isolation layer,the Q235 carbon steel substrate has a better shielding effect.According to the gray system theory,the service life of different epoxy coatings is evaluated rapidly.The results show that using BP neural network to modify the residuals of gray theory model can obtain more scientific and accurate prediction value and higher fitting degree,and provide favorable data support for paint development.