Effects of concentration and temperature on corrosion resistance of nickel base alloys in acidic environments

Abstract

The corrosion resistance of three nickel base alloys, Inconel alloys 600 and 601 and Nickel-201, has been studied in 0·01-10M H₂SO₄ at 30, 60, and 90°C. Open circuit potential (OCP) measurements at 30°C indicated the attainment of a positive OCP for alloy 601 in all concentrations of acid except in 10M H₂SO₄, while alloys 600 and 201 showed negative OCP values even in 0·01M H₂SO₄. A further negative shift in OCP was recorded for alloys 600 and 201 at 60 and 90°C. However, a positive shift in OCP was noted for alloy 601 in 10M H₂SO₄ at 60 and 90°C. Corrosion current measurements indicated better corrosion resistance for alloy 601 than for alloy 600, whereas alloy 201 showed poor corrosion resistance in all concentrations of acid. Alloy 601 showed spontaneous passivation from the corrosion potential in 0·01–1·0M H₂SO₄ at 30°C during potentiodynamic polarisation. In contrast, alloys 600 and 201 exhibited I_crit–I_pass transitions before the onset of passivation in all concentrations of acid at all experimental temperatures.