Effect of Coating Formulation on Crack Resistance of Epoxy Coatings

A cracking resistance of the epoxy coatings applied on ship's ballast tank is determined by a competition between elongation of coating films and strain induced by external structural stress and thermal stress. In this study, strain induced by thermal stress was measured and relation between thermally induced strain and coating cracking was verified. In addition, critical factors to intrinsic coating's elongation, such as resin structure and pigments, were investigated to establish the formulation technology of crack resistance ballast tank coatings. It was found that superior flexibility of coating film was attributed to high molecular weight resin and amide type curing agent which results in a low crosslink density of the resin followed by increase in mobility and flexibility. It was found that elongation of epoxy coating films increased according to decrease in pigment content and an addition of smaller particle pigment.