Crystallographic orientation of single grains of polycrystalline titanium and their influence on electrochemical processes

In electrochemical materials science, the coating of metal surfaces by oxide films plays an important role. The preparation of anodic oxide films strongly depends on the crystallographic orientation of the substrate grains which can be obtained from anisotropy-micro-ellipsometry and electron back scattering diffraction. Interference colours of the formed oxide films and electrochemical measurements on single grains of titanium prove differences in film thickness and electronic properties. Therefore, the rate of ion transfer reactions (e.g. corrosion), electron transfer reactions (e.g. metal deposition and oxygen evolution), and photo-electrochemical reactions (e.g. laser induced reactions) differ from grain to grain. Examples are discussed for anodic and thermal film formation. metal deposition and laser-induced corrosion. In clear difference to the grains, twins have a much higher activity which can be proved in cyclovoltamograms as well as with metal deposition. (C) 2003 Elsevier Science B.V. All rights reserved.