Electrodeposition of nano cobalt on a stainless steel 304 substrate using for solar energy absorber was established. Two different electrolytic bathes used in this investigation. The first bath composition is [270 g/l CoSO4, 35 g/l CoCl2, and 30 g/l H3BO3], and the second was used as the previous with addition of 2.5 g/l Co(NO3)2. The role of nitrate ions as an oxidizing agent was investigated. Different current densities (20 and 30 mA/cm2) are applied. Deposition times from 1 to 6 minutes for each current density were used. Crystal structure transformation and morphology changes were investigated for coatings at all electrodeposition conditions. SEM and EDAX are used for monitoring the gradually changes in the coated surface and nanostructure formation behavior. The degree of crystallitey and crystallite size changes was measured by using XRD device. The optical properties such as absorption and reflectivity were investigated by using UV-IR Spectrometry to discover and compromise the effect of applied electrodeposition conditions on the solar energy absorption of the formed surface coating.