Comparative study of formation and corrosion performance of porous alumina and ceramic nanorods formed in different electrolytes by anodization

• Alumina–titania coatings were fabricated by anodization in a single step.
• The universal and cheap sulphuric acid was used as the reference electrolyte.
• The minimum concentration of PTO is used to achieve ceramic nanorods.
• Dense ceramic coatings were achieved at low current density and room temperature.
• Anodized coatings show better corrosion resistance compared to bare aluminium.

Fabrication of Al2O3–TiO2 nanoceramic coatings on aluminium was carried out in a single step using cost effective sulphuric acid electrolyte with the addition of potassium titanium oxalate (PTO) by anodization method. For comparison, the anodization was also carried out in sulphuric acid electrolyte alone. The effect of composition of the electrolyte, current density and electrolyte concentration on formation and surface characteristics of anodic alumina and ceramic coatings produced from different electrolytes have been investigated. The growth process, surface morphology, nanostructure, distribution of chemical elements, phase constitutions and corrosion resistance of the coatings formed in two different electrolytes were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Tafel polarization technique and electrochemical impedance spectroscopy (EIS). As the concentration of electrolyte and current density increased, the surface properties of the coating increased up to certain content and beyond that they decreased. Dense, uniform nanoceramic coatings with less surface defects were obtained from sulphuric acid + PTO electrolyte. The corrosion studies reveal that ceramic coating formed in sulphuric acid + PTO electrolyte offers better corrosion resistance compared to the alumina coating formed in sulphuric acid electrolyte.