An electrochemical and mechanical approach to the corrosion resistance of cathodic electrocoatings under combined cyclic and DC polarization conditions

A modified AC/DC/AC test has been introduced. It consists of a combination of EIS test, cathodic polarizations, wet and dry cycles. This test method was applied to cathodically electrocoated mild steel substrates baked at different conditions. This study aims at characterizing protective behavior of under-, normal- and over-baked electrocoatings under cyclic corrosion conditions. It was found that the resistive failure is the dominant failure mechanism of all the coatings in this test. It was also found that a low crosslink density coating withstands the mechanical stresses due to dry–wet cycles better than a higher crosslink density one.