Characterization and corrosion behavior of electroless Ni-P/nano-SiC coating inside the CO2 containing media in the presence of acetic acid

In this research, Ni-P and Ni-P/nano-SiC coatings were applied on the X70 steel substrate successfully without any surfactant. Then, CO2 corrosion in the presence of acetic acid (HAc) was investigated using electrochemical techniques. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques were used for surface analyses of the coatings. The electrochemical behavior of corrosion was investigated using polarization test and electrochemical impedance spectroscopy (EIS). XRD pattern of Ni-P/nano-SiC coating was very similar to that of Ni-P coating. EDS results demonstrated the presence of SiC particles in the coating. SEM images confirmed the presence of SiC nano-particles with almost uniform distribution in the coating. The corrosion current density was less in the Ni-P and Ni-P/nano-SiC coated samples than uncoated X70 steel. Ni-P/nano-SiC coated sample had the most corrosion resistance because of less effective metallic area available for corrosive media. The overall protection mechanism of Ni-P and Ni-P/nano-SiC coatings was achieved by formation of a layer of adsorbed hypophosphite anions (H2PO2-). (C) 2010 Elsevier Ltd. All rights reserved.