Microstructure, electrochemical behaviour and bio-fouling of electrodeposited nickel matrix-silver nanoparticles composite coatings on copper

Abstract

Bio-fouling is a major cause of accelerated corrosion and premature failure of materials used in industry. This study presents synthesis, characterisation, bio-fouling, and electrochemical corrosion behaviour of Ni matrix-Ag nanoparticles based composite coatings for anti-corrosive and anti-fouling applications in sea water or marine environment. Two Ni-Ag composite coatings of compositions, Ni-0.25at.% Ag and Ni-0.75at.% Ag, were electrodeposited on copper by dispersing controlled amounts of chemically synthesised Ag nanoparticles into Ni++ bath. Effect of Ag nanoparticles on electrochemical corrosion, Ni passivation and bio-fouling of these composite coatings is highlighted. Incorporation of Ag nanoparticles into Ni matrix was found to influence texture, Ni crystallite size, and strain of the Ni-Ag composite coatings. Between pure Ni and two Ni-Ag composite coatings, Ni-0.25at.% Ag coatings exhibited the highest corrosion resistance in 3.5% NaCl owing to a synergetic combination of relatively large, strain-free Ni crystals with a pronounced texture along [111] direction. During anodic polarisation in 3.5% NaCl, Ag nanoparticles embedded into Ni matrix induced galvanic passivation of Ni phase, which improved tendency of the composite coatings for passivation. Upon exposure to sulphate reducing bacteria, these composite coatings showed greater resistance to formation of bio-film, which confirmed their anti-fouling properties. Extent of bio-film decreased with amount of incorporated Ag nanoparticles in these composite coatings. Bio-film led to a reduction in corrosion resistance of the coatings. This reduction in corrosion resistance due to bio-film decreased with increasing Ag content of the coatings. It can be concluded that anti-microbial nanoparticles embedded in a suitable metal matrix can open up new avenues in addressing bio-fouling and microbially induced corrosion in sea water.