Purpose
The ability to produce a uniform composition, high corrosion resistance with a hard coating layer during the electroless coating techniques are mainly based on the plating bath composition. The complexing agent is one of the most important components that control the coating layer properties. This paper aims to investigate the effect of the glycine as a complex agent on the surface and corrosion properties of Ni-P and Ni-P/Al2O3 electroless coating.
Design/methodology/approach
In this study, the effect of glycine as a complexing agent on the final surface and corrosion properties of the Ni-P and Ni-P/Al2O3 coatings has been investigated. The surface morphology and composition of the coated samples were investigated by scanning electron microscope (SEM) imaging and energy dispersive x-ray spectroscopy (EDS) analysis. Linear polarization scan and electrochemical impedance spectroscopy techniques were used to investigate the corrosion properties of the coating layer.
Findings
The results clarify that, glycine has a remarkable effect on the porosity content of Ni-P and Ni-P/Al2O3. It was found that increasing of glycine concentration results in higher porosity content in the coating layers. Also, the porosity in the coating layers minimizes the protectability of the coating against corrosion. The results also show that adding nano-alumina (Al2O3) to the coating path has improved the corrosion properties by decreasing the porosity in the coating layer. The scanning electron microscope (SEM) images showed that the concentration of glycine affects the content and distribution of alumina nanoparticles embedded in the coating layer. Also, it was observed that using a high concentration of glycine (0.4 M glycine), the alumina tends to agglomerate and the final alumina content in the coating was decreased.
Originality/value
The present study reveals that the quality of the final coating plays a major role in the corrosion performance of the steel substrate. The coating quality can by improve remarkably by optimization of the complexing agent used in the plating bath, to minimize the porosity involve in the coating layer.
Electroless NiP coatings use in engineering applications due to its ability to alter and improve the surface properties of the steel substrate. The present study investigates the influence of bath composition, which included nickel sulphate, sodium hypophosphite, and glycine on the deposition rate, coating roughness, and final coating microhardness with using of Taguchi techniqe. The results reveal that final coating roughness and hardness can be optimized by controlling bath composition. The achieved minimum average surface roughness (Ra) was 80.7 nm and the highest coating hardness was 1145 HV.
Electroless Ni-P coating is widely used in industrial engineering applications due to its ability to alter and improve the surface properties of the steel substrates. Electroless nickel coating introduce an excellent combination of surface properties, where, it could add brightness, luster, and good appeal. The final coating layer also possess a very good adhesion with the coated substrates, this is the reasons for using such layer as an 'undercoat' for other coatings. The ability to produce a very homogenous composition and produce coating with a high corrosion resistance are mainly based on the plating bath composition. The present work investigates the influence of bath compositions, which included nickel sulphate, sodium hypophosphite and trisodium citrate, on the process of electroless Ni-P coating. The deposition rate (Dr) as well as the bath stability were monitored to optimize the plating bath conditions with the different composition. The results of this work showed that 43
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