Combining equal-channel angular pressing and heat treatment to obtain enhanced corrosion resistance in 6061 aluminum alloy

The corrosion behavior of 6061 aluminum alloy processed by heat treatment and equal-channel angular pressing (ECAP) is investigated. Current transient, potentiodynamic polarization and electrochemical impedance spectroscopy are used to assess the corrosion resistance of 6061 aluminum alloy in different processing conditions. The results confirm that the peak-aged sample after two ECAP passes and annealed sample after four ECAP passes are the most resistant samples against corrosion. Using ECAP leads to substantial increase in the dislocation density, re-distribution of precipitates, crystallite refinement, alteration of the surface area of the cathodic sites, and increase in the volume fraction of grain boundaries that affects corrosion resistance. Assessment of the corroded surfaces of the materials shows that some coarse-grains are corroded selectively in the annealed sample leading to formation of deep and large pits on the sample surface. However, after ECAP, shallow and uniform corroded surface is observed that is in agreement with the corrosion diagrams. (C) 2015 Elsevier B.V. All rights reserved.