THE INFLUENCE OF THIN MULTI-LAYER OXIDE COATINGS MADE BY EB-PVD, ON THE CORROSION OF 316 L STAINLESS STEEL

Abstract

Corrosion is a process of destroying metals (alloys) under the chemical or electrochemical action of the environment. A valuable method to improve the corrosion resistance of metals and alloys working under extreme environments based on protecting the metal substrate with different ceramic materials has been proposed. Experiments were performed by Electron Beam – Physical Vapor Deposition (EB-PVD), for deposition of multi-thin oxide layers of the type: Al2O3 / ZrO2 doped with Y2O3 / La2Zr2O7 / ZrO2 doped with Ce2O3, on 316L stainless steel laminated sheet substrates. The influence of multi-layer oxide coatings on the corrosion of 316L stainless steel was studied by electrochemical corrosion experiments (linear polarization) in NaCl solution of different concentrations (from 0.06M to 0.6M). To highlight the microstructural aspects on the elec-trochemically corroded samples, scanning electron microscopy (SEM) analyses were performed. The coating adhesion was evaluated by scratch test. Complex multi-layer oxide coatings improve the corrosion resistance of stainless steel in dilute NaCl electrolyte solutions (0.06M and 0.2M). In contrast, for more concentrated NaCl solutions (0.4M and 0.6M), these thin multi-layer oxide coatings are more susceptible to corrosion than simple alumina coatings which have higher po-larization resistance and lower corrosion rates.