The effect of heat treatment on corrosion of C45 mild steel coated with WC-Co-Al2O3 cermet composite were examined. The cermet coatings (CC) were produced by electrospark deposition (ESD) technology. The content of aluminum oxide (Al2O3) was changed between 5 and 15 wt.%. The scanning electron microscope (SEM) was employed for the observation the surface of materials. The structure of coatings were depended from the composition of electrospark electrodes. A metallurgical bonding between the

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... ing and substrate was obtained. Thermogravimetric measurements showed a significant effect of Al2O3 content on the increase of resistance to chemical corrosion of the substrate. Additionally, heat treatment of the tested coatings were made for a temperature of 400 or 800 0 C. Heat treatment at 400 0 C of WC-Co-Al2O3 cermet coatings does not affect the structure of the tested coatings. On the other hand, after heat treatment at 800 0 C of WC-Co-Al2O3 coatings lose their anticorrosive properties. Therefore, the chemical corrosion rate of C45 mild steel coated with WC-5Co-15Al2O3 coating increases more than four times compared to the material of the same specimen treated at 400 0 C.