Electropolishing and chemical passivation of austenitic steel

Purpose: The aim of the paper is investigations a dependence between the parameters of the electrochemical treatment of austenitic steel and their electrochemical behavior in Tyrod solution. Design/methodology/approach: Specimens (rode 30 mm × Ø1 mm) were to give in to the surface treatment-mechanically polishing, electrolytic polishing and passivation with various parameter. Electrochemical investigations concerning the corrosion resistance of austenitic steel samples were carried out by means of the potentiodynamic and electrochemical impedance spectroscopy method. Findings: The analysis of the obtained results leads to the conclusion that chemical passivation affects also the chemical composition of the passive layer of steel and changes its resistance to corrosion. Electrolytic polishing improves corrosion resistance, as can be proved by the shift of the value of the corrosion potential and breakdown potential of the passive layer and the initiation of pittings. Research limitations/implications: The obtained results are the basis for the optimization of anodic passivation parameters of the austenitic steel as a metallic biomaterial. The future research should be focused on selected more suitable parameters of the electrochemical impedance spectroscopy test to better describe process on the solid/ liquid interface. Practical implications: In result of the presented investigations it has been found that the best corrosion resistance can be achieved thanks to the application of electrolytic polishing of the steel in a special bath and chemical passivation in nitric (V) acid with an addition of chromic (VI) acid temperature t = 60°C for one hour. Originality/value: The enormous demand for metal implants has given rise to a search for cheap materials with a good biotolerance and resistance to corrosion. Most commonly used are steel implants assigned to remain in the organism for some limited time only. It was compare two electrochemical methods: potentiodynamic polarization and electrochemical impedance spectroscopy.