A Comparison of Corrosion Test Methods for Painted Galvanized Steel

Various galvanized steels, ZINCROMETAL and cold-rolled steel were painted with automotive-type paints and tested via accelerated, atmospheric and on-vehicle tests. Tests indicate that the ASTM B117 salt fog test and the Kesternich SO₂ test do not yield results which are indicative of automotive, in-service corrosion performance. A modified Volvo scab corrosion test was found to offer an accelerated method to accurately predict automotive, in-service corrosion performance. Galvanized steels exhibited corrosion resistance which was far superior to ZINCROMETAL and cold-rolled steel. Thicker zinc coatings on steel were found to offer better corrosion protection to painted substrates.