Corrosion Behavior of Stainless Steels in Sulfuric Acid Containing Cl^- and Fe³⁺

Abstract

Through the chemical analysis of the environment of smoke stacks and down-hole for thermal power plants, it was clarified that sulfuric acid dew point environment was the one where there were much amount of Cl^- and Fe³⁺ with the range of 10-1000ppm besides H₂SO₄. Then, effect of Cl^- and Fe³⁺ and alloying contents (Cr, Ni, Mo, Cu and N) on corrosion behavior of various stainless steels in H₂SO₄ environment were studied by immersion test and polarization curve measurements. By analyzing these data, corrosion rate of stainless steels in 50mass% H₂SO₄ with 1000ppm Cl^- and Fe³⁺ can be expressed as the following general corrosion resistance index (GI); GI=-[Cr]+3.6[Ni]+4.7[Mo]+11.5[Cu].