Eletrodeposição e caracterização de revestimentos de Zn e Zn-Co obtidos a partir de solventes eutéticos à base de cloreto de colina e ureia para proteção contra corrosão

Abstract

Zn and Zn-Co coatings were electrodeposited on 1020 steel using a Deep Eutectic Solvent based on choline chloride and urea in a molar ratio of 1 to 2. Voltammetric experiments showed that the reduction peak of the Zn2+ species was shifted from – 1,37 V to –1,24 V in the presence of cobalt species Co2+, indicating that the Zn-Co codeposition was favored by the addition of Co2+ to the baths. Micrographic and chemical composition analyses showed that the layer morphology and Co content were sensitive to the Co2+ concentration in the bath and to the deposition potential. By varying the Co2+/Zn2+ concentration ratio, a significant difference in the deposit morphology was observed between granular and compact surfaces. X-ray diffraction patterns showed that an adequate Co content in the layers reduced the crystalline structures by five times, leading to crystals of the order of 22,3 nm. Finally, corrosion tests in 3,5% NaCl show that the Zn92Co08 coating obtained with bath III at 353 K and electrodeposited at –1,40 V reduced the corrosion rate by up to 40 times compared to the pure Zn layer.