Magnesium and its alloys like AZ91 are used for various automotive, military and aviation applications. Nanocomposite coatings on AZ91 show significant improvement in the surface properties like wear resistance, hardness and corrosion properties. Electroless coatings have unique physicochemical and mechanical properties, for which they are being used increasingly. Most applications of the electroless coatings are based on their wear and corrosion resistance. However, the characteristic like luminescence has a great potential indefence and aerospace applications. In this research, surface roughness of AZ91 magnesium alloy due to nanocomposite coating processes of ENi–B–TiO2 is experimentally investigated. It has been observed that as concentration of second-phase (TiO2) particles increases, the surface roughness of coatings also increases.