Electrochemical properties and self-healing processes of multilayer metal-filled coatings during exposure in an aggressive environment

Abstract

As part of the development of the concept of creating "smart" adaptive polymer anticorrosive coatings, the kinetics of electrochemical properties of thin- and thick-layer multilayer Zn-filled coatings at various temperatures from 23 to 60°C during prolonged exposure up to 150 days in 3% NaCl were studied. It is shown that at low temperatures and, consequently, low corrosion rates of zinc (Zn) filler, it is advisable to increase the thickness of highly filled composite coatings with active solid-phase additives in order to reduce porosity and create conditions for a restorative increase in impedance. Activation of the self-healing process in multilayer coatings can be realized with an increase in temperature. So already at 40°C, the impedance begins to grow over the entire frequency range. At the same time, an increase in the ohmic component in the high-frequency (HF) region is recorded, with a simultaneous drop in capacitance and an increase in the phase anglemodulus up to 86°, which indicates an increase in the hydrophobicity of the coating material. In parallel, the activation of tread properties is observed. The results obtained show that optimization of the coating design, in particular multilayering, combined with acceleration of coating’s internal diffusion and corrosion processes, make it possible to give the coating "smart" properties by implementing adaptive impedance growth and blocking defects with a corroding metal dispersed filler while significantly extending the period of antocorrosion protection.