An Accelerated Intergranular Corrosion Test for Detecting Sensitization in Low Chromium Ferritic Stainless Steels

The procedure for developing an accelerated corrosion test which would aid in assessing the sensitization resistance of low chromium ferritic stainless steels is described. Immersion corrosion tests were conducted on Fe-Cr binary alloys in boiling acidified Cu-CuSO₄ solutions. Reducing the H₂SO₄ concentration of the standard ASTM A262E solution results in a reduction in the minimum chromium content required for passivation. In a boiling solution containing 0.5 w/o H₂SO₄ + 6 w/o CuSO₄ + Cu chips, alloys with >12 w/o chromium are passive and alloys with < 12 w/o chromium undergo general attack. The 0.5 w/o H₂SO₄ solution is shown to be useful in evaluating the time-temperature-sensitization behavior of a 12 w/o chromium ferritic stainless steel.