The effect of viscoelastic Parameters on the Protective performance of the Epoxy Coatings Using Creep-Recovery Modeling

Investigation of rheological parameters on the protective performance of an epoxy coating through wet and dry cycles has been studied using creep-recovery modeling. For this purpose, an epoxy resin was cured with four types of hardeners (Polyamine-based, Polyamidoamine-based, Polyether polyamine-based, and Cycloaliphatic Polyamine-based hardener) to achieve various adhesion behaviors and viscoelastic properties. The storage modulus, viscoelastic creep-recovery, permeability, electrochemical parameters, and glass transition temperature were determined. Samples were exposed to humidity chamber and adhesion was measured at wet and dry conditions over time. After drying, adhesion loss and recovery were evaluated by the pull-off test. The electrochemical behavior of coatings was studied by electrochemical impedance spectroscopy (EIS). It was found that the higher the elastic module, the more the adhesion loss. Recovery of adhesion after wet and dry cycles correlated with the reversible element of creep and recovery data. After that, creep recovery data were modeled and for the first time, two rheological parameters (viscose ratio and the elastic ratio of the viscoelastic behavior) were defined for predicting adhesion durability. A coating with a higher viscose property in creep recovery behavior shows week adhesion recovery . It may referred to irreversible strain in a coating that cannot be recovered after the elimination of stress. Additionally, it was found that a sample with excellent initial protective properties, higher elastic modulus, and low initial water permeability may quickly fail because of the adhesion failure after wet cycles.