High pitting corrosion resistance of pure aluminum with nanoscale twins

Pure aluminum coating with a nanoscale twin structure (NT Al) was successfully deposited by using a magnetron-sputter technique. The corrosion behavior of the NT Al was investigated and compared with that of cast Al in an aqueous acidic chloride solution by using potentiodynamic polarization and an electrochemical noise technique. The results indicated that for NT Al, both the cathodic and anodic reaction processes were greatly inhibited, the corrosion potential shifted to a more positive value, and the corrosion current density apparently decreased. The NT structure affected the pitting behavior of pure aluminum in two ways based on the stochastic analysis of the electrochemical noise data: (i) the formation rate of metastable pits was accelerated and (ii) the growth of the stable pit was impeded. This leads to the enhancement of the pitting resistance for NT Al coatings.