The Effect of CeCl3 as an Inhibitor on the Localized Corrosion of AA2024-T3 as a Function of Temperature

Abstract

Cerium inhibition of localized corrosion of AA2024-T3 as a function of temperature is evaluated based on the electrochemical characteristics of synthesized intermetallic compounds (IMCs) using a microcell method. Corrosion morphology studies of secondary phase particles in AA2024-T3 subjected to similar conditions are also presented. In a 4 mM Ce3+-containing solution, the anodic characteristics of IMCs are similar to those in a NaCl solution without any inhibitors at all temperatures tested, indicating Ce3+ is not an effective anodic inhibitor. Strong suppression of cathodic kinetics occurring on IMCs is observed in the presence of Ce3+ at all test temperatures. The inhibition efficiencies on cathodic reactions are similar at 30 and 50°C, but become weaker at 70°C. Electrochemical analysis indicates that inhibition provided by Ce3+ depends on the kinetics of local pH increases and the subsequent formation of Ce hydroxide on the surface, making Ce a slow inhibitor. The sluggish inhibition kinetics are amplified at high temperature (>50°C). The initial dealloying corrosion of S-phase cannot be inhibited at ambient temperatures. This effect becomes more severe at high temperature (>50°C). Trenching corrosion around Al-Cu-Mn-Fe type particles can be well suppressed with addition of Ce3+ at temperatures up to 50°C.