The aim of this research is the optimization of Ni-P Electroless Plating on Al7075 alloys by the heattreatment. The influence of various factors such as heattreatment time an temperature, thickness of coatings, preparing conditions (sand blasting and Zn intermediate layer) on engineering properties of coatings were evaluated e.g. adhesion, wear resistance, load ability, crystallinity of coatings. For analyzing of results various equipments such as SEM, XRD, EDAX, optical microscope, micro hardness was used. For wear study Pin on disk procedure was applied. The results showed that although at high heattreatment temperatures, the hardness was increased but to achieve appropriate adhesion between coating and substrate the range of 300 o C is suitable. Heat treated specimens at 300 o C for 9 hours showed that the optimum adhesion and wear resistance. Adhesion tests on specimens with various preparing conditions showed that sand blasting and Zn intermediate layer increased the adhesion. Studies on Ni-P electroless coatings in various thickness showed that the optimum thickness to approach the best adhesion and wear resistance was about 50 Micron. Heattreatment at 150, 200, 250, and 300 o C for 1 hour didn’t show any crystalline structure but at 300 o C for 9 and 16 hours, Ni 3 P crystals were formed. At 350, 400, 450 and 500 o C for 1 hour, the amount of crystalline phase was increased. The studies on X-ray patterns showed that the grain size of crystalline structure was about 30 nanometers.
