Effect of deposition time on morphology, corrosion resistance and mechanical properties of Ti-containing conversion coatings on zinc

Ti-containing conversion coatings were obtained on zinc electroplated steel. The influence of deposition time on the coatings morphology, chemical composition, corrosion resistance and mechanical properties were studied. Their chemical composition strongly depends on deposition time. As the time increases from 5 s to 300 s, the Ti content decreases and the Si content increases. For the deposition time of 5 s the Si:Ti atomic ratio in the conversion coating is 0.32 and after 300 s it increases to 9.1, which is accompanied by reduction in corrosion resistance. As deposition time increases, the microhardness of the coatings and their wear resistance deteriorate. Corrosion test results show that the coatings can be applied to protect zinc against corrosion.

► Chemical composition of Ti-containing conversion coatings depends on deposition time.
► The time growth up to 300 s results in a decrease of Ti and an increase Si content.
► Differences in chemical composition cause the variation in corrosion resistance.
► Coatings obtained in 20 s have the highest wear resistance and microhardness.
► The Ti-containing coatings can be applied to protect zinc against corrosion.