Corrosion behavior of Iron Surface Immersed in Acidic Electrolyzed Water

Abstract

Anodically electrolyzed dilute NaCl or Na₂SO₄ solution (NaCl or Na₂SO₄ acidic electrolyzed water) shows high redox potential and dissolved oxygen concentration, also the former generates free chlorine. We have evaluated the characteristics of both acidic electrolyzed water, and immersed iron in an acidic electrolyzed water, HCl, or H₂SO₄ of the same pH (=2.48). Then compared dissolution rate, discussed effect of free chlorine or dissolved oxygen on corrosion behavior. As a result, corrosion rate of iron immersed in NaCl acidic electrolyzed water is as much as 3.5 times that in HCl at the same pH, furthermore, free chlorine in NaCl acidic electrolyzed water accelerates the dissolution rate and increases the surface roughness of iron. Corrosion rate in Na₂SO₄ acidic electrolyzed water is as much as 3.4 times that in H₂SO₄ at the same pH. Dissolved oxygen is major factor for iron dissolution, however, it is likely another factor may promote iron dissolution except dissolved oxygen. Immersed iron with thermal-oxide film in NaCl or Na₂SO₄ acidic electrolyzed water, thermal-oxide film was dissolved with underlaying iron, the surface, exhibited natural-oxide film, was as same as that was immersed in HCl similarly. We can conclude that acidic electrolyzed water has the possibility to use etching or pretreatment instead of HCl or H₂SO₄ conventionally used.