Comportement à la corrosion électrochimique de revêtements quasi-cristallins préparés à la torche plasma

Electrochemical corrosion behaviour of quasicrystalline coatings prepared by plasma torch

¹ Laboratoire de Physico-Chimie des Matériaux, Université de Provence, Marseille
² Laboratoire de Science et Génie des Matériaux Métalliques (CNRS URA 149), Ecole des Mines, Nancy

Abstract

Over the last years, new alloys containing aluminium and various transition elements were prepared. These materials are original because they show quasicrystalline phases. A lot of papers have been devoted to their atomic and electronic structures, as well as to their mechanical properties. But although, they were discovered almost ten years ago, their applications were only considered recently. These applications are linked with their abrasion resistance, their hardness and their anti-adhesive properties. Moreover, the mechanical properties only are not enough to permit the use of a material: their corrosion resistance must also be studied.

In view of the application of quasicrystalline coatings to the manufacture of cookware, the corrosion behaviour of different coatings was studied in dilute acetic acid solution at a temperature of 95°C. The coatings were prepared, on carbon steel, by plasma torch spraying of atomized powder. Different investigations as : electrochemical tests using direct and alternative current, analysis of the solutions, X-ray diffraction were carried out. It was pointed out that the annealing treatments were beneficial to increase the corrosion resistance. Annealing causes the decrease of the coating defects and leads to the formation of a decagonal phase which we suppose to be less reactive than the initial icosahedral phase. Comparison to stainless steels shows that the corrosion performance of the treated coatings are intermediate between austenitic and ferritic steels.