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Erosion corrosion of alumina thin films deposited on AISI 4140 and obtained by varying potential bias

Abstract:

This paper presents the results variation of potential bias (0, -40, -60 and -100 V dc) of Al2O3 deposited on AISI 4140 steel substrates by magnetron sputtering method using a target DC reactive aluminum (99.9%) in an atmosphere composed of Ar/O2 to a substrate constant temperature of 300°C. The coatings were evaluated compared to corrosion, erosion and erosion-corrosion an impact angle of 90° and a solution of 0.5 M NaCl and silica, analyzing the effect of potential bias (0, -40, -60 and -100 V dc) Al2O3 coatings. The electrochemical characterization was performed using the technique of electrochemical impedance spectroscopy (EIS), optical microscopy (OM) was used to determine the morphology after the electrochemical evaluation. Nyquist diagrams for dynamic corrosion and erosion corrosion show a capacitive behavior with a high impedance module and two time constants. By decreasing the potential bias was generated an increased resistance to polarization, both for mechanisms dynamic corrosion and corrosion erosion.