High tensile strength steels used for the outdoor constructions are required to possess a good atmospheric corrosion resistance. The specimens of high tensile strength steels containing various amounts of C, Si, Mn, Cr, Ni, Mo, Ti, Nb, Zr, B, and Cu were exposed to the atmosphere at Amagasaki and Kitakyushu up to five years. The effects of the alloying elements on the atmopheric corrosion resistance of the steels were analysed by means of the multiple regression analysis.
Corrosion rates of the steels are expressed by the equation,
whre w: corrosion loss (μ), t: exposure time (year) andk, n: constants. kandkare given by the following equations.
k(μ)=182.2-54.7 Si-41.6 Cr-11.1 Ni-87.0 Mo-39.8 Cu-52.2 Nb
k(μ)=247.9-106.6 Si-28.4 Cr-27.5 Ni-65.4 Mo-41.2 Cu-7071B
n(year)=2.90-1-2.4Si-0.32 Cr-0.74 Mo-42.50 P-77.64B
where Si, Cr etc. indicate the contents of the alloying elements in wt %. The effects of the alloying elements on the pitting depth were also analysed; Si, Ni, and Cu reduced the depth of pits.