Heat Treated NiP–SiC Composite Coatings: Elaboration and Tribocorrosion Behaviour in NaCl Solution

Tribocorrosion behaviour of heat-treated NiP and NiP–SiC composite coatings was investigated in a 0.6 M NaCl solution. The tribocorrosion tests were performed in a linear sliding tribometer with an electrochemical cell interface. It was analyzed the influence of SiC particles dispersion in the NiP matrix on current density developed, on coefficient of friction and on wear volume loss. The results showed that NiP–SiC composite coatings had a lower wear volume loss compared to NiP coatings. However, the incorporation of SiC particles into the metallic matrix affects the current density developed by the system during the tribocorrosion test. It was verified that not only the volume of co-deposited particles (SiC vol.%) but also the number of SiC particles per coating area unit (and consequently the SiC particles size) have made influence on the tribocorrosion behaviour of NiP–SiC composite coatings

CO2 corrosion of bare steel under an aqueous boundary layer with oxygen

The effect of dissolved carbon dioxide on steel corrosion in aerated solutions has been variously reported, ranging from "no effect'' to "catalytic enhancement of corrosion. ''A corrosion model was developed, verified with published experimental data, and then used to interpret the role of carbon dioxide in the presence of oxygen. Carbon dioxide has little effect on the corrosion rate when its pressure is less than the oxygen pressure. The model reveals that the effect becomes significant only when the carbon dioxide pressure is substantially higher than the oxygen pressure. The results also show that for a thick boundary layer, carbon dioxide hydration controls the corrosion rate at low oxygen pressures. As oxygen pressure is increased, oxygen dominates corrosion with oxygen diffusion contributing to and then controlling the corrosion rate. For a thin boundary layer, charge transfer of oxygen reduction controls the corrosion rate