Cobalt-phosphorus-titanium oxide nanocomposite coatings: structures, properties, and corrosions studies

摘要

Chromium coatings are largely restricted in electrical and electronic industries due to the environmental concerns. To address these concerns, a cobalt-phosphorus-titanium oxide (Co-P-TiO2) nanocomposite coating is developed in this study using a nanoparticle-reinforced electrodeposition process. The effects of TiO2 nanoparticles on the properties of co-deposited Co-P-TiO2 nanocomposite coatings are investigated. The surface characterisation is carried out by scanning electron microscopy and atomic force microscopy, while the crystal structure is studied using X-ray diffraction. The mechanical properties of nanocomposite coatings including microhardness and wear resistance are also determined. To study the electrochemical behaviour of the coatings, the potentiodynamic polarisation analysis combined with electrochemical impedance spectroscopy is performed. The Co-P-TiO2 coating at 1 g/L TiO2 addition displays the best physicochemical performance. Compared to Co-P coating, the mechanical properties of the nanocomposite coating are significantly improved by the strengthening effects of the well-dispersed TiO2 particles. Excellent corrosion resistance is also achieved for the Co-P-TiO2 at proper TiO2 addition due to its smooth and defect-free microstructure. However, it is found that the excessive addition of TiO2 decreases the coating quality, resulting in an unfavourable microstructure and properties.