CORROSION RESISTANCE OF Cr(III) PASSIVATED ZINC ELECTRODEPOSITS

Abstract

In this research, corrosion resistance of the Cr(III) passivated zinc
electrodeposits was evaluated by the neutral salt spray test and electrochemical
methods. The zinc electrodeposits were passivated in some different Cr(III)
passive solutions, resulting in different colors of passive layers. The results of the
neutral salt spray test showed that the iridescent Cr(III) passivated sample was
the most corrosion resistant with 768 hours of testing for reaching 5% white rust
area. These results agreed with those of the electrochemical methods that the
iridescent Cr(III) passivated sample was also the most corrosion resistant with
the lowest corrosion current density of 1.59µA/cm2 and the highest passive layer
resistance of over 33.89kΩ.cm2. The corrosion resistance of the passivated
samples decreased in the order of the iridescent passivated samples, the whiteblue passivated samples, the black passivated samples and finally the
unpassivated samples.