The Effect of CeCl3as an Inhibitor on the Localized Corrosion of AA2024-T3 as a Function of Temperature

Cerium inhibition of localized corrosion of AA2024-T3 as a function of temperature is evaluated based on the electrochemical characteristicsofsynthesizedintermetalliccompounds(IMCs)usingamicrocellmethod.CorrosionmorphologystudiesofsecondaryphaseparticlesinAA2024-T3subjectedtosimilarconditionsarealsopresented.Ina4mMCe 3 + -containing solution, the anodic characteristics of IMCs are similar to those in a NaCl solution without any inhibitors at all temperatures tested, indicating Ce 3 + is not an effective anodic inhibitor. Strong suppression of cathodic kinetics occurring on IMCs is observed in the presence of Ce 3 + 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 Ce 3 + 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 Ce 3 + at temperatures up to 50 ◦ C.