Comparison of Corrosion Behavior of Thin Layers from Copper, Aluminum and Chromium

Abstract

The aim of this research is to determine the corrosion resistance on superficial layers laid-down through electrical sparking on the steel carbon OLC 45 samples, the used electrode being made from corrosion resistant material (Aluminum, Copper and Chromium). The superficial treatment through impulse electrical discharges is a procedure through which the proprieties of the metallic materials can be improved. The proprieties of the superficial layers obtained through this procedure are the same as the electrodes material being used or very close to this one, the properties resulting from micro alloying and the diffusion of the electrode material in the sample of steel. The experiments were done, for the superficial treatment through impulse electrical discharges, using Al, Cu and Cr electrodes. The corrosion speed was determinate through electrochemical corrosion. The corrosion potential and marking the polarization curves (linear and cyclic) was determined with an advanced electrochemical system type VOLTALAB 32. The acquisition and processing of experimental data was made with the help of the specialized software VOLTMASTER 2. The corrosion potential was determined by tracing the curves of linear polarization, recorded in sea water, using the Evans coordinates: E = f (log I). The corrosion process analysis was made also based on the cyclic polarization curves. The fine determining of the topography surfaces exposed to the action of the corrosive environment was made using the atomic force microscope (AFM). The support but also the sparking probes, has present the same type of corrosion; a general corrosion, which in the initial moments is represented by the appearance of corrosion dots. The superficial layers laid through Cr, Al and Cu electrodes sparking proves a improved corrosion resistance to see water compared to the base steel. Aluminium has the highest corrosion tendency while copper has the best protection.