Synergistic effects of passivation treatment and nano-electrodeposition technologies on corrosion protection performance of the electrogalvanized steel

It is well known that surface nanocrystallization and passivation treatment are effective ways of improving corrosion resistance properties of the electrogalvanized steel, but their synergistic effects have rarely been studied. In this study, the effect of surface nanocrystallization on the chromium-free passivation film of electrodeposited zinc coating is investigated. Meanwhile, the formation mechanism of the chromium-free passivation film on electrodeposited zinc coating changing with the reduction of grain sizes from micro to nano-meters is analyzed and a model for the formation mechanism is proposed. The chromium-free passivation film of nanocrystalline zinc coating combines the advantages of passive films and nano-materials, and has better corrosion protection performance than the chromium-free passivation film of coarse-grained zinc coating and nanocrystalline zinc coating as well as a mirror decorative effect with light blue color. The corrosion resistance properties of coarse-grained zinc coating are heightened almost five times due to the synergistic effects of passivation treatment and nano-electrodeposition technologies.