A Study on Corrosion-Resistant Properties of Unleaded Bi-Containing Automotive Epoxy Primers

Abstract

The aim of this work is to evaluate the difference in the corrosion resistance between unleaded containing bismuth automotive epoxy primers and leaded one. It was also discussed the effect of zinc phosphate pretreatment. The specimen coated unleaded epoxy primer showed 0.5V higher corrosion potential than that of bare steel. The result of salt spray test did not indicate remarkable difference of corrosion resistance in all specimens above 10 thickness up to 1200 hours. In the cyclic corrosion test, unleaded epoxy primers on phosphated substrate performed good corrosion properties until 800 hours. The lead free primer performed the equivalent corrosion resistance as leaded coating on phosphated steel, but slightly inferior to that of leaded on bare steel. These results show that the pre-treatment of zinc phosphating is effective as well as pigment changing in performing anti-corrosion properties in automotive bodies.