A practically important scenario in the corrosion of aluminum (Al) alloys is the variation in damage characteristics, i.e. mode, rate and morphology, as function of environmental temperature. In order to address this problem from a mechanistic point of view, this paper presents results for corrosion potentials, pitting potentials and electrochemical characteristics for intermetallic particles commonly present in high strength aluminum alloys, for tests conducted in 0.1M NaCl of varying temperature. Tests were conducted between 0 and 60 • C via the use of a micro-capillary electrochemical cell. The intermetallics investigated were Mg 2 Si, MgZn 2 , Al 7 Cu 2 Fe, Al 2 Cu, Al 2 CuMg and Al 3 Fe. Analysis of the results reveals that the electrochemical behavior of such compounds is heavily dependent on temperature, with ramifications for localized corrosion (and protection) In the most general sense, corrosion represents the adverse intersection between a material and the environment; while in the case of aluminum (Al) alloys, their prescription is widespread and covers many environmental exposure conditions. For a given material, the environment is responsible for the type and extent of corrosion that may result; warranting an investigation of the electrochemical characteristics as function of environment. [1][2][3][4][5][6] In an attempt to unambiguously characterize the mechanistic aspects of localized corrosion of heterogeneously structured high-strength Al-alloys, we have presented the electrochemical characteristics for a number of intermetallic particles and phases common to a large range of such alloys, [7][8][9][10] paying particular attention to the effect of chloride concentration 9 and the effect of solution pH.7 This approach has also recently been followed for investigation of the second phases that occur in magnesium alloys.
11It has been shown that both [Cl − ] and pH have a significant effect upon the corrosion morphology and rate of bulk Al-alloys, as demonstrated for AA7075-T651. 12 Of key relevance to the work herein, it was shown that the resultant alloy corrosion was able to be reconciled in terms of both morphology and rate, from knowledge of the individual electrochemical characteristics of the alloy constituents.13 Furthermore, it is of importance to note that the associated electrochemical kinetics upon alloy constituents is not trivial, in that kinetics may not be accurately predicted based upon composition or knowledge of corrosion potentials alone. However, polarization testing was able to reveal significant quantitative insights allowing a leap in understanding the origins of localized corrosion (and in some cases the absence of localized corrosion). Examples include; spontaneous passivity of Mg 2 Si at alkaline pH and the increase in the ability of Fe-containing intermetallics to sustain ORR as either pH or [Cl − ] increase, to name but a couple of important factors. 7,9 Similarly, such richness is not predicted by methods such as SKPFM, which has been previously used to predict loca...
