Influence of the cathodic intermetallics distribution on the reproducibility of the electrochemical measurements on AA5083 alloy in NaCl solutions

The corrosion behavior of alloy AA5083 in solutions of NaCl at 3.5% is controlled by the density of the cathodic precipitates of Al(Mn,Fe,Cr) present in the alloy. These precipitates are not distributed homogeneously over the surface of the alloy. Further, their presence conditions the electrochemical response of the alloy. For these reasons, in order to guarantee the reproducibility of electrochemical tests on this alloy, it is necessary to determine the minimum surface area exposed to the medium which represents the average behavior of the system. In the-present study, a systematic analysis has been conducted on the degree of reproducibility of electrochemical tests as a function of the area of surface exposed, for the alloy AA5083 in solutions of NaCl at 3.5%. A high dependence between the dispersion of the electrochemical data and the exposed area has been established. This behavior contrast with those of other alloys, like AA1050, which is not conditioned by the values of exposed area. This has been related to the much lower cathodic precipitates density in this alloy. (C) 2002 Elsevier Science Ltd. All rights reserved.