Effect of Alloying Elements on Perforation Corrosion Resistance of Hot Rolled Steel for Automotive Bodies

The effect of alloying elements on perforation corrosion of mild steel was studied by cyclic corrosion tests and an outdoor exposure test. Ultra low C-P-Cu hot rolled steel has been alloy-designed for the perforation corrosion resistance application for the automotive bodies.The newly designed TS 45 kgf/mm2 steel, produced in the mill, shows the excellent mechanical properties and an equivalent paintability to a low C mild steel. In addition, the perforation life time of the developed steel is about twice longer than that of the mild steel, according to a cyclic corrosion test conducted on automotive underbody parts.Its excellent resistance to perforation corrosion was considered to be achieved by the formation of a protective rust layer of amorphous species, judging from the results of rust analysis by EMPA, FT-IR and laser Raman spectrometer.