Microstructure and corrosion-resistance performance of Ni-Cr alloy coatings by direct and pulse current electrodeposition

Abstract:

Ni-Cr alloy coatings were obtained on mild carbon steel surface by direct current (DC) and pulse current (PC) electrodeposition. X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) and atomic force microscope (AFM) were used to analyze the phase structure and surface morphology. The corrosion behaviors of Ni-Cr alloy coatings in the 3.5% (mass fraction) NaCl were investigated by soak method and electrochemical polarization method. The results show that microstructure and performance of the coatings were greatly affected by electrodeposition methods. The pulse electrodeposition can increase the amounts of new nuclei and reduce grain size, so the PC alloy coatings exhibit a relatively uniform and fine structure. The self-corrosion potential (Ecorr) of PC alloy coatings is increased from -0.624V to -0.477V and the corrosion current density (Icorr) is decreased from 1.911?0-4 A.cm-2 to 3.789?0-5 A.cm-2 compared to those of the DC alloy coatings. The PC alloy coatings have better corrosion resistance than DC alloy coatings.