Evaluation of the Accelerated Aging Properties of Anti - Corrosive Coatings for Inner Cavity of Automobile

Abstract

According to the characteristics of the actual service environment of inner cavity of automobile, the damp heat test, salt spray test and electrochemical AC impedance technology were used to evaluate the coating and establish the aging kinetic equation. Results showed that under the accelerated aging test, the coating was intact within 600 h of the damp heat test and 360 h of the salt spray test. The failure aging of the inner cavity coating in 3.5% (mass fraction) NaCl solution at 25 ℃ could be divided into three stages: the initial stage , the middle stage and the late stage of aging; the initial stage of aging (the 0th to 2nd cycle) had good corrosion resistance, and low frequency electrochemical impedance|Z| 0.01 Hz was on the order of 109 Ω·cm2 or more; in the middle stage (the 4th to 6th cycle), |Z|0.01 Hz was on the order of 105～108 Ω·cm2, the size and quantity of internal micropores increased, and the corrosion resistance was obviously attenuated; in the late stage (8th cycle), local bulges appeared on the surface, |Z|0.01 Hz was on the order of 105 Ω·cm2 and below, and the coating failed. Based on this, establishing the aging kinetic equation could predict and evaluate the service life and protective performance of the inner cavity anti-corrosive coatings.

Keywords

• inner cavity of automobile|anti-corrosive coatings|accelerated tests|aging kinetics|electrochemical impedance