AN XPS STUDY OF THE CORROSION BEHAVIOR OF SPUTTER-DEPOSITED AMORPHOUS AL-W ALLOYS IN 1-M HCL

The surfaces of sputter-deposited amorphous Al-15W and Al-45W alloys immersed or anodically polarized in 1 M HCl solution were analysed in connection with their corrosion and anodic polarization behavior. These alloys passivated spontaneously and were more corrosion-resistant than pure aluminum metal. Similarly to tungsten metal these alloys were immune to pitting even by anodic polarization, whereas amorphous Al-Ta and Al-Nb alloys suffer pitting by anodic polarization in 1 M HCl. The surface films were composed of an oxyhydroxide mixture consisting of aluminum and tungsten cations in the low potential region. However, anodic polarization at the high potentials led to the formation of the surface film consisting exclusively of tungsten ions as cations. The roll of tungsten in the alloying element is discussed in comparison with that of tantalum and niobium.