A corrosion study of hot-dip galvanized steel sheet pre-treated with γ-mercaptopropyltrimethoxysilane

In the present work an organofunctional silane, γ-mercaptopropyltrimethoxysilane (γ-MPS), has been deposited on hot-dip galvanized cold rolled steel from different silane solution concentrations. Painted and unpainted silane treated samples were corrosion tested and painted samples were adhesion tested. The surface chemistry of the unpainted silane treated samples was investigated with AES, ToF-SIMS and EDS and the surface morphology was studied with SEM.The results show that the silane film thickness is dependent on the silane concentration in the silane solution and a higher silane concentration gives a thicker film. Moreover, thicker films tend to give films with a pronounced crack pattern and even detachment of film debris. Corrosion tests of unpainted samples show that γ-MPS can not work as a passivation treatment but gives a very good adhesion to the paint.