Influence of phosphate layer on adhesion properties between a steel surface and an organic coating

In this paper, tests of some physico-chemical properties of protective epoxy coating on non-alloy structural steel grade type S235JRG2 have been carried out. This is a significant construction material whose use is remarkably important for many steel products such as H beam, I beam, transmission towers, steel pipe etc. Coatings represent one of the ways to protect metal from corrosion. The properties of coating thickness, hardness, gloss, and adhesion were investigated. The same properties were tested by exposing the sample non-alloy steel plates to corrosive conditions of the salt and humid chamber and seawater. Part of the samples prior to application of the coating were immersed to phosphate solution to further investigate the effects of phosphatization on the properties of the coating. After exposure of the plates to the humidity chamber conditions, no traces of corrosion products, cracking or peeling of the coating were found on the surfaces. The plates tested in the sea water and salt chamber showed a minor damage on protective coating. The traitability properties were tested by the Pull off Adhesion test. Force pull adhesion off test shows less value for unphosphated samples than for phosphated ones.