Electrochemical Corrosion Behavior of High Chrome Ferritic Stainless Steel 447 in Concentrated H₂SO₄ Solution

Electrochemical techniques were used to investigate the electrochemical corrosion behavior of high chrome ferritic stainless steel 447 in 85%-98% (mass) H₂SO₄ solution at 40-80℃. The results show that the stainless steel 447 presented a corrosion characteristic of periodical activation-passivation in 85%-95% H₂SO₄ solution at 80℃. This kind of electrochemical oscilation was caused by the formation and dissolution of p type semiconductor passive film produced in spontaneous passive state and coupled with the electrochemical reaction. The corrosion resistance of the high chrome ferritic stainless steel 447 decreased with the increase of temperature and the decrease of H₂SO₄ content in 85%-98% H₂SO₄ solution at 40-80℃. With the increase of the temperature, the oscillation increased; when the mass fraction of H₂SO₄ was less than 98%, the oscillation increased with the increase of H₂SO₄ content, while the mass fraction of H₂SO₄ was no less than 98%, stainless steel 447 could get static passive state in H₂SO₄ solution, and the corrosion of stainless steel 447 in spontaneous passive state was controlled by charge transfer step.