Trivalent chromium electrodeposition using a deep eutectic solvent

Purpose - This paper aims to investigate the electrolytic deposition of corrosion-resistant chromium coatings from a trivalent chromium plating bath based on deep eutectic solvent, a new generation of room temperature ionic liquids. Design/methodology/approach - The electrolyte contained chromium (Ill) chloride, choline chloride and the additive of extra water. The surface morphology was estimated by means of SEM technique. The microstructure of as-deposited and annealed coatings was studied using X-ray diffraction method. The kinetics of the chromium electrodeposition and the corrosion electrochemical behavior of the coatings were investigated by cyclic voltammetry technique. Findings - Chromium coatings with an amorphous type of microstructure are electroplated from this bath. Some carbon and oxygen are included in deposits obtained. The step-wise mechanism of the electrochemical reduction of Cr(III) ions to Cr(0) is detected. The current efficiency in this system sufficiently exceeds that typical of usual aqueous electrolytes. The coatings fabricated using plating bath based on deep eutectic solvent showed enhanced corrosion resistance in an acidic medium: there is no current peak of active dissolution in polarization curve and the corrosion potential shifts to more positive values as compared with "usual" chromium. Originality/value - The electrodeposition of chromium coatings from an environmentally acceptable trivalent chromium electrolyte, a deep eutectic solvent containing chloride choline and extra water additive has been investigated for the first time.