Development of Multilayer Surface Coating on a Brass Foil

Brass foils have several desirable mechanical and physical properties. However, these brass foils are prone to corrosion and dezincification. Presence of a small amount of zinc in brass causes micro-cracks in high-pressure and corrosive environment. Surface modification through a protective coating is necessary to improve the corrosion resistance and mechanical properties of brass. In this regard, electroless Ni-B coating emerged as a promising surface coating process. Electroless coating benefits include homogenous deposition on an even/uneven surface, direct deposition on a catalytic surface, less porous structure, increased corrosion resistance, simple and cost-effective procedure. In the current study authors have developed a protective Ni-B coating through electroless deposition (ELD) process over a brass foil of 100 µm thickness. Since, brass substrates are not catalytically active, a nickel (Ni) layer was first deposited all over the brass foil through electroplating (ED) process to obtain a catalytically active surface. After that, Ni-B coating was deposited over the Ni layer using the ELD process. X-RD spectrum of ELD Ni-B coating showed a broad peak of Ni, indicating the presence of amorphous phases. Top surface morphology of developed ELD coating, shows uniform nodular grains and crack free surface. During heat treatment at 450 ℃ in air, the nodular grains grow in size. After heat treatment, several sharp peaks associated with a crystalline nickel and nickel boride phases (Ni2B and Ni3B) were detected. Ni-B coated Brass foil shows improvement in the hardness value (568 ± 50 HV0.1) as compared to brass foil.