Synthesis and properties of electrodeposited Ni-B-CeO2 composite coatings

Ni-B coatings are extremely hard and wear resistant with decent anticorrosion properties which make them suitable for automotive, aerospace, petrochemical, plastic, optics, nuclear, electronics, computer, textile, paper, food and printing industries. However, further improvement in properties is essential to address more challenging requirements and new developments. In the present study, Ni-B and novel Ni-B-CeO2 composite coatings were electrodeposited (ED) on mild steel substrates using dimethylamine borane (DMAB) as a reducing agent. A comparison of properties of Ni-B and Ni-B-CeO2 coatings is presented to elucidate the useful role of CeO2 addition. The structural analyses indicate that Ni-B coatings are amorphous in their as deposited state. However, addition of CeO2 into Ni-B matrix considerably improves the crystallinity of the deposit. The surface morphology study reveals the formation of uniform, dense and fine-grained deposit in both Ni-B and Ni-B-CeO2 composite coatings. However, Ni-B-CeO2 composite coatings exhibit high surface roughness. The nano mechanical properties show that the addition of CeO2 particles into Ni-B matrix results in remarkable improvement in mechanical properties (hardness and modulus of elasticity) which may be attributed to dispersion hardening of Ni-B matrix by CeO2 particles. The electrochemical polarization tests confirm that the addition of CeO2 improves the corrosion resistance of Ni-B coatings. This improvement in corrosion behavior may be ascribed to the reduction in active area of Ni-B coatings by the presence of inactive CeO2 particles into Ni-B matrix.