Abstract
St-37-type steel samples were pretreated with Cr(III) and Cr(VI) conversion coatings (CC). The Cr(III) pretreated samples were then posttreated by Co(II) and Ni(II) CC. The corrosion resistance of the samples was studied using direct current (DC) polarization technique and electrochemical impedance spectroscopy (EIS) in 3.5 wt% sodium chloride (NaCl) solution. The morphology and elemental composition of the pretreated steel samples were studied using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Results showed that Cr(VI) and Cr(III) CC can improve significantly the corrosion resistance of the steel sample. It was shown that Cr(VI) can improve corrosion resistance of the steel sample more than the Cr(III) one. It was revealed that Co(II) and Ni(II) CC can improve significantly corrosion resistance of the Cr(III) pretreated sample.
