Corrosion Behavior of 6101 Aluminum Alloy Strands for Automotive Wires

Abstract

International audienceMicrostructural states produced by each step of the manufacturing process leading to the production of automotive strand arms in 6101 aluminum alloy (AA6101) for wiring harnesses were investigated in relation to their corrosion behavior in NaCl solution. The observed corrosion morphology,i.e., pitting corrosion or intergranular corrosion, was strongly dependent on the precipitation state, i.e., mainly the presence of intergranular Mg2Si precipitates. A ‘grain size – corrosion resistance’ relationship was also evidenced with an ennoblement of the corrosion potential for wires heavily cold drawn, which were characterized by a nanometric grain size. Dislocation density as well as the homogeneity of alloying element distribution were also found to be relevant parameters for explaining the electrochemical behavior of each microstructural state. Plastic deformation and recrystallization phenomena occurring during the manufacturing process were found to be associated with redistribution of alloying elements, which impeded the formation of intergranular Mg2Si precipitates. Therefore, in the present study, the cold drawing process was found to increase the intergranular corrosion resistance of AA6101

Influence of equal-channel angular pressing on the microstructure and corrosion behaviour of a 6xxx aluminium alloy for automotive conductors

“…9), SEM observations showed that Fe-rich IMCs acted as cathodes with respect to the matrix, therefore enhancing the preferential dissolution of the latter in NaCI solution. Such a behaviour has been largely reported in the literature and explained referring to differences in composition between IMCs and the surrounding matrix [23,24,70,71]. In that sense, considering only those OM and SEM ob servations, no modification of the corrosion mechanisms at the OCP and after polarisation in the anodic domain was apparent after ECAP by comparison to the as-received sample, which agreed with the literature [28,72].…”

Unravelling the characteristics of Al-alloy corrosion at the atomic to nanometre scale by transmission electron microscopy

“…Of the limited studies to date on IGC, a discrepancy exists in Cu-free alloys [14-17, 21-23, 42]. A few studies reported that upon artificial ageing, Cu-free 6xxx Al-alloys suffered IGC as result of the formation of Mg 2 Si precipitates along grain boundaries [14][15][16][17]42]. In contrast, these alloys were also reported to be immune to IGC though Mg 2 Si precipitates form along grain boundaries [21][22].…”

“…Nanoscale Mg 2 Si precipitates play a dominant role in increasing the strength of Cu-free 6xxx Al-alloys [1][2][9][10][11][12]. However, these alloys suffer IGC with the evolution of Mg 2 Si precipitates along grain boundaries during ageing [13][14][15][16][17]. Electrochemical tests were performed upon synthesised Mg 2 Si bulk specimens, and also through the electrochemical microcell technique on microscale Mg 2 Si particles in the Al-matrix [18][19].…”

Evolution of pitting corrosion resistance and mechanical properties in ultrafine-grained commercially pure aluminium during annealing

“…The fragmentation of intermetallic particles during SPD processing can contribute to an improvement in corrosion resistance [25], due to the formation of a more stable passive film and a reduction in microgalvanic currents [23,26]. On the other hand, an increased number of particles due to SPD processing may result in an increase in the corrosion rate due to the elevated number of pit initiation sites, as was shown for commercially pure aluminium after equal channel angular pressing (ECAP) [26] or AA6061 after cold drawing [27], both of which were examined in NaCl solution.…”