A new approach to estimates the adhesion durability of an epoxy coating through wet and dry cycles using creep-recovery modeling

Estimation of adhesion durability of an epoxy coating through wet and dry cycles has been investigated. For this purpose, we endeavor to find a correlation between adhesion durability and viscoelastic parameters of coatings. An epoxy resin was cured with four types of hardeners (polyamine, polyamidoamine, polyether polyamine, and cycloaliphatic polyamine-based hardener) and a mixture of two hardeners (polyether polyamine and cycloaliphatic polyamine) in four different mixing ratios (20:80, 50:50, 70:30, 90:10) to achieve various viscoelastic properties. The storage modulus, viscoelastic creep-recovery, electrochemical parameters, and glass transition temperature were determined. Adhesion loss and recovery of adhesion were measured under wet and dry conditions during the time. It was found that creep recovery data correlated exactly with the recovery of adhesion. Creep recovery data were modeled and for the first time, two rheological parameters (viscous ratio and elastic ratio) were defined to predict adhesion durability. Pearson correlation coefficient was used as a statistical measure of the strength of a linear relationship between the paired data. It was found that adhesion durability and recovery of adhesion after wet and dry cycles have a strong linear relationship with viscous and elastic ratios. A coating with a higher viscous behavior in creep recovery tests acts more weakly in the recovery of adhesion. It may be referred to as irreversible strain in a coating that may not be recovered after the elimination of stress.