Temperature dependences of the electrochemical parameters of adaptive composite polymer coatings during long-term exposure in corrosive media

The effect of temperature variation on the electrochemical characteristics of individual adaptive epoxy polymer coatings (PCs) and composite systems consisting of two adaptive layers with different active additives was studied. It was shown that the mechanism of spontaneous impedance growth under natural conditions of exposure in a corrosive environment without any additional external impact can be operative in adaptive composite PCs. A correlation between the kinetic dependences of changes in the impedance modulus and in the potential of the substrate under the coating was identified. It was found that at the stages of growth and stabilization of the potential and impedance modulus (up to 500 days of exposure in 3% NaCl), a strong dependence of the substrate potential on the measurement temperature exists. It was shown that the electrochemical characteristics of a composite coating with two adaptive layers of different materials are significantly higher than those of an individual adaptive PC. The effect of growth in activation energy of ion transfer through the coating was found for the composite PC both on inert platinum (Pt) and on corroding steel (St3) substrates. It was shown that an adaptive composite bilayer coating on corroding St3 substrate can have more stable electrochemical characteristics than a similar coating on inert Pt substrate.