In this paper, we first reported the formation of viscous layer during the anodic electrolytic etching process of Mg alloys and NdFeB magnets in AlCl3-1-ethyl-3-methyl-imidazolium chloride (AlCl3-EMIC) ionic liquid at high current density. The electrodeposition of protective Al coating on Mg alloys and NdFeB magnets was carried out after the electrolytic etching. The formation of viscous layer resulted in the complete removal of surface oxides, which dramatically improved the adhesion of the protective coatings to substrates. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.006201esl] All rights reserved.