Corrosion behavior and passive film chemistry of 216L stainless steel in sulphuric acid

摘要

Corrosion behavior and chemical structure of the passive film of a newly developed 200 series austenitic stainless steel (216L) were studied in sulfuric acid (H₂SO₄) and compared with 316L. From potentiodynamic polarization studies it was found that the corrosion behavior of 216L closely follows that of 316L. The breakdown of passivity was evaluated by addition of sodium chloride (NaCl). The immersion tests revealed that the corrosion rate of 216L in various concentrations of H₂SO₄ at ambient temperature is equivalent to 316L. X-ray photoelectron spectroscopy (XPS) analysis of the passive film formed on 216L revealed enrichment of Cr ions on the surface while Mo and N compounds were also present. Ni and Mn ions were conspicuous by their absence in the passive film.