WC-Ni composite coatings were prepared on the mild steel substrates by high temperature sinter brazing. Potentiodynamic polarisation was performed on the coated sample immersed in 3%NaCl solution. Two limited current plateaus appear in the anodic polarisation curve. The first limited current plateau is attributed to the formation of Ni and Cr oxide, while the second corresponding to W oxide. The surface morphology observation and composition analysis after anodic polarisation were investigated by the scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy. The elemental concentrations in the immersion solution were studied with inductively coupled plasma (ICP) spectroscopy. It shows that the selective dissolution of Ni base binder alloy as well as the electrochemical dissolution of WC exists during the anodic polarisation process.

The corrosion behaviors of AA6061 alloy in ethylene glycol (EG)–water solution were investigated by weight‐loss test and electrochemical measurement. The surface morphology observation and composition analysis were performed by scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX) spectroscopy. After weight‐loss test, the pH of EG–water solution increased. The presence of glycolic acid (GA) enhanced the corrosion susceptibility of AA6061 alloy. The higher pH value intensified the aggressive action of GA to AA6061 alloy. GA forms a complex with aluminum ions and its negative charge centers of oxygen atom plays a key role for the complex formation.