Electrodeposition of Co-Cr Black Coatings on Steel in Deep Eutectic Solvents, for Solar Collection Applications
Abstract
The electrodeposition of Co-Cr black coatings on AISI 304 stainless steel substrates was studied using a solution of Co and Cr salts in an ionic liquid as electrolyte. The electrolyte was prepared employing choline chloride (ChCl) and ethylene glycol (EG) in molar ratios of 1:2, 1:8 and 1:16, as well as Co and Cr salts in molar ratios of 1:1, 2:1 and 4:1. The electrodeposition times were 30, 45 and 60 min. Cyclic voltammetry was used in order to define the potential window in an interval from -1.93 to 1.12 V. The electrodeposition was carried out by chronoamperometry. Scanning Electron Microscopy (SEM) was used to characterize the microstructure and chemical composition of the coatings. Their optical properties were characterized by using UV-Vis spectroscopy and Fourier-Transform Infrared spectroscopy (FT-IR). Homogeneous black coatings having absorptivities (α) of 0.98 and emissivities (ε) of 0.03 were obtained, which were suitable for their application in solar thermal collectors.
Keywords
Black co-cr coatings, Deep eutectic solvents, Optical properties.