Effect of titanium oxide ceramic particles concentration on microstructure and corrosion behaviour of $$\text {Ni}$$–$$\text {P}$$–$$\text {Al}_{{2}}\text {O}_{{3}}$$–$$\text {TiO}_{{2}}$$ composite coating

Composite coatings are coatings that have been considered in terms of properties, such as corrosion resistance, oxidation resistance and excellent hardness. In this study, (hbox {Ni})–(hbox {P})–(hbox {Al}₂hbox {O}₃)–(hbox {TiO}₂) composite coating was made on AISI 316 steel using direct current deposition technique. The microstructure of the coating and its corrosion resistance were studied by changing the amount of titanium oxide (1, 2, 3 and (4~hbox {g l}^-1)) in the bath. To investigate the morphology of the coating and the analysis of the coated material, a scanning electron microscope (SEM) and EDS microscopy were conducted, respectively. The results showed that in the bath containing (4~hbox {g l}^-1) titanium oxide, the coating is perfectly uniform and continuous, while by reducing the amount of titanium oxide, it is not possible to form a suitable coating on the entire surface of the substrate. To investigate the corrosion resistance, the potentiodynamic polarization and electrochemical impedance spectroscopy tests in aqueous solution of 3.5% NaCl were carried out on coated and uncoated samples. The results of these tests were also correlated with microscopic images and showed that the coatings in a bath containing (4~hbox {g l}^-1) titanium oxide has the highest corrosion resistance.