Synthesis and properties of electrodeposited Ni-B-Zn ternary alloy coatings

Abstract

Ni-B coatings have decent properties like high hardness, wear resistance and decent anti-corrosion properties which make them suitable for automotive, aerospace, petrochemical, textile and electronics industries. Despite these promising properties, further improvement in their properties is essential in order to address more challenging requirements and new developments. Taking a note of above consideration, novel Ni-B-Zn coatings have been synthesized. In the present study, a comparison of properties of Ni-B and Ni-B-Zn coatings in their as deposited state is presented to elucidate the effect of zinc addition on structural, thermal, mechanical and electrochemical properties. The coatings were deposited on mild steel substrates through conventional electrodeposition process using dimethylamine borane (DMAB) as reducing agent. The structural analyses (XRD) indicate that Ni-B coatings amorphous in as deposited condition. However, the addition of zinc to Ni-B results in improvement in crystallinity. The study of surface morphology through SEM and AFM reveals the formation of uniform, dense and fine-grained deposits in both the coatings. However, addition of Zinc increases the roughness of the Ni-B matrix. It is also noticed that nanomechanical properties of Ni-B coatings are significantly improved by the addition of zinc due to solid solution strengthening nickel-boron matrix with zinc. The electrochemical polarization tests indicate that incorporation of zinc into Ni-B matrix shifts the Ecorr and Icorr to more positive values and thus demonstrates a decent reduction in the corrosion rate of the coatings.