Intergranular Corrosion Penetration in AA5083 (UNS # A95083) as a Function of Electrochemical and Metallurgical Conditions

A coordinated experimental and modeling study of selected factors influencing intergranular corrosion (IGC) penetration depth into AA5083 is presented. Potentiostatic tests at -0.73 VSCE in 0.6 M NaCl solution were conducted on LT, ST, and LS surfaces of sensitized AA5083. The IGC penetration rate was found to depend on applied potential, degree of sensitization (DoS), exposure time, and propagation direction relative to the rolling direction. Depths of IGC penetration were characterized through metallographic techniques, microscopy, and image analyses. The results were analyzed to describe the IGC depth distributions and to serve as input data for a set of descriptive models that can estimate IGC damage progression for AA5083 during exposure to 0.6 M NaCl at pH 8.3. This set of descriptive models was validated with 94% accuracy for 100oC sensitization. Extension of this combined experimental and modeling approach to 80oC sensitization demonstrated that sensitization temperature is another significant factor.