| This dissertation presents a comprehensive electrochemical study aimed at determining the factors that control the corrosion evolution of the important structural alloy Aluminum 2024-T3. An important aspect of corrosion in this alloy is copper redistribution. The redistributed copper serves to enhance the kinetics of the corrosion process and presents some major difficulties with respect to the development of new families of conversion coatings. A new quantitative electrochemical technique, based on underpotential deposition of lead on copper, was developed to assay the surface coverage of copper. Two major sources of copper available for redistribution are discussed: the S-phase (Al2CuMg) and copper in solid solution. In each case, a dealloying mechanism is responsible for liberating copper that becomes available to redistribution by solid state and/or liquid phase transport mechanisms. This dissertation is concerned with identifying the relative importance of these sources of copper and the active transport mechanisms. In order to decouple the sources of copper, synthetic 2024 alloys were designed that emulate the oxygen reduction kinetics of the real alloy. The results obtained indicated that, in principal, both sources of copper were operative during redistribution and, for the particular alloy that was examined, both contributed about equally to the amount of redistributed copper. |
