Electrochemical Behavior and Surface Chemistry of Aluminum Alloys: Solute-Rich Interphase Model

Abstract : The electrochemical behavior of physical-vapor-deposited nonequilibrium stainless Al-W and Al-Ta alloys and the electrochemical behavior and surface chemistry of sputter-deposited nonequilibrium stainless Al-Ta alloys have been investigated. Results from the vapor-deposited alloys show that these materials possess enhanced passivity despite the presence of nodules and other defects. The stainless aluminum alloys that exhibit better performance are the sputter-deposited thin films that more uniform. Sputter-deposited Al-Ta alloys exhibit enhanced passivity over a pH range of 2 to 12 even though the passive film chemistry varies considerably over this range. This enhanced passivity can be explained by the solute-rich interphase model (SRIM), which claims that formation and passivation of occluded cells are controlled by localized concentrations of solute. The higher concentrations of solute at the metal-oxide interface and around occluded cells stabilize the passive film from continued chloride attack and dissolution.