Inhibition of Stress Corrosion Cracking of Sensitized AA5083

The stress corrosion cracking behavior of sensitized aluminum alloy 5083 (AA5083) was studied by slow strain rate testing in 3.5 wt% NaCl solution with and without the addition of K2CrO4, Na2SiO3, or NaVO3 as corrosion inhibitors. Sensitized AA5083 was very susceptible to intergranular stress corrosion cracking (IGSCC) at the open circuit potential (OCP) in the solution with no inhibitor. However, it became immune to IGSCC in the orientation tested when the added inhibitors shifted the OCP to a potential below the breakdown potential (E-b) of the beta phase. Chromate and vanadate inhibited IGSCC in this fashion, whereas silicate did not. Sensitized AA5083 samples exhibited severe IGSCC when polarized above the E-b of the beta phase during testing, even in the presence of chromate. When the samples were polarized below the E-b of the beta phase, ductility was fully recovered with no evidence of IGSCC. A high rate of beta-phase dissolution, which is essential for IGSCC, can be prevented by shifting the OCP below the E-b of the beta phase.