Electrochemical behaviour of Fe–20Cr–5Al and Fe–20Cr–5Al–0 · 3Y alloys in aqueous solutions

The corrosion behaviour of Fe–20Cr–5Al and Fe–20Cr–5Al–0 · 3Y in three aqueous solutions including 3 · 5 wt-%NaCl, 3 · 5 wt-%NaCl z 1 · 5 wt-%Na₂ S₂ O₃ and 10 wt-%H₂ SO₄ were investigated by electrochemical techniques. The results showed that Fe–20Cr–5Al–0 · 3Y exhibited better corrosion resistance than Fe–20Cr–5Al in NaCl solution. When Na₂ S₂ O₃ was added in the NaCl solution, as expected, the two alloys suffered more serious localised corrosion, however, Fe– 20Cr–5Al–0 · 3Y alloy exhibited better corrosion resistance than Fe–20Cr–5Al. Two alloys exhibited active–passive transition and trended toward general corrosion when tested in H₂ SO₄ solution. The corrosion current densities for each alloy corroded in H₂ SO₄ solution were higher than that corroded in NaCl and NaCl z Na₂ S₂ O₃. Meanwhile, the addition of a small amount of Y in Fe– 20Cr–5Al alloy increased the corrosion resistance of this alloy in H₂ SO₄ solution. The corrosion mechanisms of two alloys and the effect of Y addition on the corrosion behaviour of Fe–20Cr–5Al are discussed.