Patent ID: 7731896

Claim:
A low alloy steel excellent in hydrochloric acid corrosion resistance and sulfuric acid corrosion resistance, characterized in that said steel contains C: 0.001 to 0.2%, Si: 0.01 to 2.5%, Mn: 0.1 to 2%, Cu: 0.1 to 1%, Mo: 0.001 to 0.12%, Sb: 0.01 to 0.2%, Ni: 0.1 to 1%, P: 0.05% or less, S: more than 0.005% to less than 0.012%, N: 0.001 to 0.007%, and Cr: 0.1% or less, with the balance being Fe and unavoidable impurities; and the acid corrosion resistance index AI, which is calculated from the following expression <1>, of said steel is zero to 75, AI/ 10,000=0.0005+0.045×Sb %−C %×Mo % <1>, where % means mass %.