Plasma electrolytic Oxidation (PEO) is a new method of forming ceramic coatings on light metals such as Al, Mg, Ti, etc. and their alloys. But, it is very difficult in fabricating ceramic coatings on steel using a single PEO technique. To overcome this problem, hot-dipped aluminum (HDA) was treated by PEO technique in this paper, and multilayer composite coatings which consisting of Fe-Al layer, Al layer, and Al_2O_3 layer were formed on steel substrate. Structures, micro-mechanical properties, and fa...