Effects of CeO2 addition on corrosion resistance and microstructure of the Ni-base coatings

Nowadays، there is considerable attention to use of Ni-base coatings on steel because of its high corrosion resistance in various corrosive environments; there is still a considerable void in our knowledge of the influences of additives on corrosion and microstructure of these coatings. Besides، using of Ni-base pack cementation method has been very attractive because of its low-cost and ability to coat complex shapes and even the internal surfaces of the samples. For these purposes various amounts of CeO2 (1wt%، 3wt% and 5wt%) was added to the Ni-base (NiCrBSi) (56% Ni، 24% Cr، 7. 5% C، 4. 5% Fe، 4. 5% Si، 3. 5% B) raw materials. The pack cementation coating method were used on a mild steel substrate. SEM، XRD، optical microscopy and X-ray diffraction analysis methods were used to characterize the coats. Moreover polarization dynamics corrosion test was also used to study of corrosion in a 3. 5%t NaCl solution. The results showed that Ni-base pack cementation coats are more corrosion resistance. Besides، the corrosion rates were decreased with increasing the CeO2 contents in the coat. By comparing the percent inhibition of samples coat a sample of 5% cerium cementation found that the criterion of 86% is the maximum percent inhibition.