Effect of Current on Corrosion Resistance of Duplex Stainless Steel Layer Obtained by Plasma Arc Cladding

In order to repair or strengthen stainless steel structural parts, the experiment was conducted by using plasma arc cladding technology to prepare 2205 duplex stainless steel (DSS) layers on the surface of Q345 steel. Their macro morphology and microstructure were observed by an optical microscope and the phase composition of microstructure was analyzed by an X-ray diffractometer instrument (XRD). The electrochemical behavior of 2205 DSS cladding layer under different current in 3.5% NaCl etching solution was studied by the potentiodynamic polarization, the electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectrometer (XPS). The results showed that when the current was 100 A, the forming of cladding layer was continuous, complete and fine with the dilution ratio of 11.43%. The mass ratio of austenite to ferrite in the microstructure increased with the increase of current and it was up to the optimum of 1.207 with the current of 100 A. Under such conditions, the self-corrosion potential of the cladding layer was up to the maximum while its corrosion current density reached the minimum, thus the corrosion resistance of the cladding layer reached the optimum. It was attributed to the existence of a large amount of Cr3+ and Mo6+ in the passive film of cladding layer, which can stabilize the passive film and promote the formation of Cr2O3 in the passive film.