Evaluation of antibacterial activity of anticorrosive electroless Ni–P coating against Escherichia coli and its enhancement by deposition of sono-synthesized ZnO nanoparticles

• Mild steel surface was plated by anticorrosive electroless Ni–P composite coating.
• ZnO NPs were deposited on the external surface of Ni–P deposit.
• Biological activity of the resultant surfaces was evaluated against Escherichia coli.
• Electroless Ni–P layer showed partial biological activity.
• Deposition of ZnO NPs effectively prohibited the bacterial colonization.

The adhesion and proliferation of bacteria on metallic surfaces in different places such as health centers, industries and even homes increase the risk of human infections. In the present research, mild steel as a substrate was coated with a Ni–P layer through electroless plating to prevent surface corrosion of the steel. In order to achieve an antibacterial metallic surface, simultaneous sono-synthesis and deposition of ZnO nanoparticles (NPs) were performed on this Ni–P coating. The morphology and chemical composition of the ZnO coated plate were characterized by the use of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The X-ray diffraction (XRD) pattern confirmed that the ZnO was pure and showed a hexagonal structure. The antibacterial activity assay of the electroless Ni–P coating against Escherichia coli O157:H7 showed some biological activity but the plate containing ZnO NPs effectively prohibited the growth of E. coli. It is concluded that the attached ZnO surface could be utilized for antibacterial purposes by reduction of colonization.

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