Protective conversion nanocoatings for hot-dip galvanized steel

Over the course of this work, the physicochemical and mechanical properties of coatings were investigated in order to find good alternatives to chromate coatings. It was found that zirconium- as well as cerium- and lanthanum-containing coatings are able to withstand exposure to both high and low temperatures without the degradation of their protective characteristics. It was established that the thickness of the zirconium[1]containing coatings amounts to 170 nm, whereas the thickness of the cerium- and lanthanum-containing coatings is 210 nm. It should be noted that the thickness of the chromate layers is much higher and is in the range of 200…1000 nm. It was also established that cerium- and lanthanum-containing coatings formed in a manganese sulfate containing solution have the best protective ability among the coatings developed – 82 hours before the appearance of the first foci of white rust, which is higher than the time until the appearance of the first centers of white rust mandated by international standards for chromate coatings. It has been established that zirconium-containing coatings are suitable as an adhesive sublayer for further paint or varnish application.

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