Effect of curing process and pyrolysis temperature on the microstructure, adhesion and corrosion resistance of PCS-derived coatings

Polycarbosilane-derived (PCS-derived) coatings were fabricated on iron substrate by dip-coating method. The effects of curing process including air curing and divinylbenzene (DVB) curing and pyrolysis temperature on the coating microstructure, adhesion and corrosion resistance in 3.5 wt% NaCl solution were systematically studied. Both curing process and pyrolysis temperature have a significant influence on the micro-cracks, surface roughness and ceramicization of the coatings. PCS-derived coatings fabricated by air curing process has the lower micro-crack width due to the higher curing degree. No matter in which curing process, the average micro-crack width and surface roughness of the coatings pyrolyzed at 600 °C are higher than those of the coatings pyrolyzed at 400 °C or unpyrolyzed. Electrochemical test results indicate that all coatings can protect the iron substrate from corrosion. The corrosion resistance of the PCS-derived coating is dominated by the microstructure including micro-cracks, surface roughness and ceramicization. Coatings fabricated through air curing and pyrolyzed at 400 °C have better corrosion resistance due to less micro-cracks, lower roughness and higher ceramicization. Corrosion resistance mechanism of the PCS-derived coatings was also analyzed.