Effect of stabilising heat treatment on characteristics of electrolytic alumina coating on ferritic stainless steel

摘要

The effect of stabilising thermal treatment on the characteristics of conversion coatings modified by electrolytic alumina deposits have been studied using SIMS analysis and X-ray diffraction in grazing incidence. Before heating, alumina deposit obtained is in form of amorphous boehmite gel. Heat treatment at 800 ℃ in air leads to a very uniform coating morphology and induces diffusion phenomena. After heating (24 h), the coating is constituted of two layers: an alumina (δ-Al{sub}2O{sub}3) outer layer and a chromium oxide (α-Cr{sub}2O{sub}3) inner layer. At the coating/steel interface mixed oxide (iron, chromite) are present. The electrolytic alumina deposit blocks the chromium oxide in the deep zone.