Evaluation of corrosion resistance of Znx-Mn1-x coatings electrodeposited on 1020 carbon steel rotating electrode from choline chloride and urea at eutectic composition

Abstract

Znx-Mn1-x coatings were successful electrodeposited on a rotating 1020 carbon steel electrode from an electroplating solution prepared by the mixture of choline chloride (ChCl) with urea (U) with the molar ratio of 1:2 (1ChCl:2U) and without the addition of additives. Their corrosion performances of the electrodeposited coatings were evaluated in 3.5% NaCl solution by open circuit potential (Eoc) monitoring, potentiodynamic polarization and linear polarization around Eoc. The chemical analysis of the electrodeposited coatings showed that the Mn electrodeposition was inhibited with the increase of the electrode rotation rate. The images of the surface morphologies showed that the increase in the rotation promoted grain refinement, producing more homogeneous surfaces with nodular grains. The X-ray diffraction patterns revealed crystalline structures with distinct phases of Zn and Mn, indicating the joint electrodeposition of Zn and Mn did not produce the formation of intermetallic phases. The Znx-Mn1-x coatings had better corrosion protective performance than the Zn coating. Finally, the Zn84Mn16 coating was best, presenting in the immersion tests a lifetime 3 times longer than the pure Zn coating.