In this research, surface properties of single layer NiP and NiB and hybrid NiB/NiP coating were applied successfully on Al 5052 substrate. NiP and NiB coatings were applied by electroless plating method and in acidic and basic bath, respectively. NiP with different phosphorou content obtained in acidic bath by varying the pH in the range of 3.9 to 6.5 that leads to high, medium and low phosphorous content in the NiP coating but with the same thickness of 30 ?m. On the other hand to obtain NiB coating in basic bath, pH were set 13 and adjust the parameter to take NiB coating as the same thickness of NiP coating.in order to obtain hybrid coating of NiB/NiP , two basic and acidic bath were applied respectively with the 15 ?m thickness for each layer and overall thickness of 30 ?m. Evaluating the surface properties were studied by using Scanning Electron Microscope (SEM), Optical Microscope(OM), Vickers microhardness testing machine, X-ray diffraction analysis and corrosion testing machine. The result of evaluating the surface morphology of NiP coating with different in phosphorous content indicates that increasing in phosphorous content of coating leads to finer cauliflower morphology and lower roughness. On the other hand NiB morphology were studied and same result as NiP coating were obtained. However NiB coatings porosity and roughness are more because of its high deposition rate. Studies show that in NiP coatings , increase in phosphorous content from low phosphorous (3.8% wt) to medium phosphorous (6.75 % wt) decrease corrosion resistant characters of density and potential from 3.45 ?A/cm2 and -379 mV to 8.9 ?A/cm2 and -478 mV, respectively. More increase in phosphorous content until high phosphorous leads to extreme enhance in corrosion characters to 1.2 ?A/cm2 and -270mV. Hardness of coating also were investigated in the NiP coating with low, medium and high phosphorous and show 680, 590, 478 HV, respectively. Decrease in phosphorous content leads to increase in hardness which refers to coating structure. Low phosphorous was completely crystalline, medium was semi amorphous semi crystalline and high was completely amorphous. NiB hardness was 710 HV which is better than NiP coating in all phosphorous content. hardness of coatings also changed by duplexing them in which NiB/NiP(medium P) and NiB/NiP(low P) hardness decrease by duplexing to 564 and 580 HV but NiB/NiP(high P) hardness increase to 730 HV. Among the monolayer and duplex coating, NiB/NiP(high P) coating had the highest hardness value (about 730 HV) and lowest corrosion density (about 0.72 ?A/cm2) which indicated it as the best coating. Key words : Electroless coating, hybrid coating, duplex coating, Ni-P, Ni-B, corrosion resistant
