This study focuses on the effects of powder size and Ni–Al bonding layer on the electrochemical behaviour of plasma-sprayed Al2O3-13% TiO2 coating in fresh tropical seawater. The presence of the metallic bonding layer reduces the coating porosity and increases the surface roughness for both microparticle and nanoparticle coatings. The nanoparticle exhibits better corrosion rate of 1.9×10−6mmpy compared to the microparticle coating, with a corrosion rate of 3.05×10−6mmpy. However, the presence of the metallic bonding layer increases the corrosion rate for both micro and nanoparticle coatings. The corrosion mechanism for the coating with and without the metallic bonding layer is discussed in detail.