Electrochemical corrosion evaluation of new Zn-Sn-In coatings electrodeposited in a eutectic mixture containing choline chloride and ethylene glycol

Ternary Zn-Sn-In coatings were successfully electrodeposited for the first time on 1020 carbon steel substrates from a choline chloride and ethylene glycol base bath to improve the corrosion resistance of Zn-Sn alloys. The micrographs of the coatings revealed that increasing the concentration of indium (In) in the alloy reduced the grain size, and the electrodeposition performed at –1.3 V produced denser and more compact coatings rich in Zn. The diffractograms showed the deposition of metallic Zn, Sn, and In, as well as the presence of an In-Sn4 intermetallic phase. The electrochemical corrosion tests in 3.5% NaCl solution showed that the addition of indium in the Zn-Sn coatings increased the corrosion resistance of the protective layer, with the Zn64Sn23In13 coating, electrodeposited at –1.3 V, showing corrosion resistance superior to the other investigated coatings.