Dresden 2011 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 12: Postersitzung I

MM 12.34: Poster

Monday, March 14, 2011, 17:30–19:00, P5

Phocphate Crystallisation — •Paul Schneider, Andreas Erbe, and Frank Renner — Max-Planck-Institut für Eisenforschung, Düsseldorf, Deutschland

Chemical reactions forming surface coatings are an important way to protect metals against environmental attack. Besides the relevance for applications, there is a considerable fundamental interest in the nucleation of crystals on surfaces in complex environments. As modern steels contain silicon and aluminium as elements forming passive layers, phosphate crystal growth under acidic conditions on surfaces of aluminium, silicon, and steels containing silicon and aluminium has been investigated. Different fluoride treatments were employed. On Silicon(100) with native oxide layer, a strong etching of pits was observed, with only few phosphate crystals formed on the surface. Results on a steel with aluminium/silicon coating also show a strong etching, and deposition of fluorides on the surface. Differences between pure aluminium and silicon on the one and surfaces in which aluminium and silicon coexists are attributed to the coexistence of metallic and semiconducting crystalline structures in the initial surface. Such coexistence leads to a substantial modification of the pickling attack.