Correlation between water diffusion and adhesion loss: Study of an epoxy primer on steel

Epoxy adhesion to steel is known to be weakened by the presence of water.In this study, a fusion bonded epoxy primer is applied on mirror-polished steel and immersed at 60 °C in deionised water. A correlation is then made between the time of diffusion of water through the primer to the steel epoxy interface and the adhesion loss after immersion evaluated by pull-off test.First, a water diffusion and permeability study on epoxy primer films has been performed to achieve accurate estimation of the time needed for water to reach the interface. Then, adhesion tests after ageing of the epoxy primer applied on steel were used to estimate the time associated to the loss of adhesion.