Properties of electrodeposited Ni-B-ZrO2 composite coatings

Abstract

Ni-B coatings have high hardness and high wear resistance which make them suitable for automotive, aerospace, petrochemical, textile and electronics industries. Further improvement in properties (especially the corrosion behavior) will extend their range of applications and thus make them suitable to high wear and severe corrosion applications of oil and gas industries. Taking a note of above consideration, novel Ni-B-ZrO2 coatings were synthesized. In the present study, a comparison of properties of Ni-B and Ni-B-ZrO2 coatings in their as deposited state is presented to elucidate the effect of ZrO2 addition on structural, surface, thermal and electrochemical properties of binary Ni-B coatings. Mild steel samples were used as substrate material and the coatings were deposited through conventional electrodeposition process using dimethylamine borane (DMAB) as reducing agent. It is noticed that the addition of ZrO2 has a significant influence on crystal structure, surface roughness, thermal properties and corrosion behavior Ni-B coatings. It is noticed that Ni-B coatings are amorphous in their as deposited state while addition of ZrO2 significantly improves the crystallinity. Surface analyses confirm the formation of fine and dense structures in both Ni-B and Ni-B-ZrO2 coatings. However ZrO2 addition increases the surface roughness. The electrochemical polarization tests confirm that incorporation of ZrO2 into Ni-B matrix considerably improves the corrosion resistance due to reduction in active area of Ni-B matrix.