Transitions between pitting and intergranular corrosion in AA2024

Abstract

The pitting and intergranular corrosion (IGC) behavior of various tempers of AA2024 was investigated in 1 M NaCl. The breakdown potentials associated with pitting or IGC were determined. The breakdown potentials were found to be almost independent of sample orientation for any given temper. Artificial aging had a strong effect on polarization behavior and localized corrosion morphology. The anodic polarization curves of AA2024 in the solution heat treated and water-quenched condition, T3, and T3+ tempers exhibited two breakdown potentials, whereas overaged AA2024-T8, T8+ , and solutionized and furnace cooled AA2024 exhibited only one breakdown potential. When two breakdown potentials were observed, the more active one was found to be related to the transient dissolution of S phase Al 2 CuMg particles leading to pitting while the noble one was thought to result primarily from initiation and growth of IGC. The breakdown potentials decreased with increasing aging time at 190°C, and only one breakdown potential was measured for T8 and T8+ tempers. Unlike the T3 temper, no sharp IGC was found for these tempers. Selected granular attack from breakdown of the copper-depleted matrix was believed to be the cause for localized corrosion in the T8 and T8+ tempers. The effect of nitrate and sulfate ions on the localized corrosion behavior was also studied.

A study of the mechanisms of corrosion inhibition of AA2024-T3 by vanadates using the split cell technique

“…Local cathodes associated with IMCs on the AA2024 surface could still support the ORR, even when the net current was anodic. Likewise, local anodes associated with S-phase particles could still suffer selective dissolution even when the net current was cathodic [10]. The micrographs shown in Figs.…”

“…Anodic polarization curves of AA2024-T3 in deaerated 0.5 M NaCl with no inhibitor are characterized by a double breakdown potential [10]. The first breakdown potential (E P1 ) is related to the transient dissolution of S-phase particles and the second one (E P2 ) to matrix and intergranular attack [10].…”

“…The first breakdown potential (E P1 ) is related to the transient dissolution of S-phase particles and the second one (E P2 ) to matrix and intergranular attack [10]. Fig.…”

“…The susceptibility of aluminum alloys to localized corrosion strongly depends on the distribution and electrochemical properties of the intermetallic compounds and second phase particles [4][5][6][7][8][9][10]. A great effort has been made to analyze the corrosion behavior of high strength aluminum alloys.…”

“…A great effort has been made to analyze the corrosion behavior of high strength aluminum alloys. In particular, AA2024-T3 is among the most extensively studied alloys, and the mechanisms of corrosion have been debated in the literature [5,[7][8][9][10][11][12][13][14][15][16][17].…”