Inhibitive Effects of Chromate, Molybdate, and Nitrate on Corrosion Fatigue Crack Growth Rates of AA2024-T3 in 3.5 NaCl Solution

AA 2024-T3 aluminum alloy finds wide applications in aerospace industry due to its high strength to weight ratio, good toughness and relatively good fatigue crack growth resistance. This aluminum alloy, however is suffered from pitting corrosion and corrosion fatigue crack growth rate (CFCGR) attacks. Among corrosion protections used in industrial applications, corrosion inhibitors are desirable. In this investigation, corrosion rates of AA 2024 aluminum alloy in 3.5 NaCl solution containing chromate (CrO42−), molybdate (MoO42−) and nitrate (NO3−) inhibitors were measured using a three-electrode potential method. The percentages of each inhibitor was varied at the levels of 0.1, 0.3 and 0.5. Subsequently, CFCGR tests were conducted using middle tension, M(T) crack specimens in 3.5 NaCl solution containing 0.3 inhibitors. In this study, the sinusoidal load with constant amplitude was selected whereas stress ratio, R and frequency, f used were 0.1 and 10 Hz respectively. Results of this study showed that the inhibitive effect of the inhibitors under study was ranked as follows: (CrO42−) > (MoO42−) > (NO3−). The mechanisms of CFCG under anodic inhibitors were likely controlled by the ability of inhibitors to form passive oxide films which sealed off the crack surface from the aggressive environment at the crack tip. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.