Surface characterization of titanium oxide coating on SUS304 stainless steel by electrical discharge coating

This study presents a precursor-free and additive-free method for depositing titanium oxide (TiO₂) coatings on SUS304 stainless steel using Electrical Discharge Coating (EDC) with optimized 3D-printed (additively manufactured) Ti-6Al-4V electrodes and deionized water as the dielectric. The effects of discharge currents (6–11 A) on coating morphology, thickness, and corrosion resistance were systematically examined. SEM, EDS, and XPS analyses confirmed that the overall optimal current window for stable and uniform TiO₂ coating formation is 7–9 A, with 8 A providing the most balanced performance in terms of oxide quality, surface uniformity, and corrosion resistance. At 9 A, the coating reached its maximum thickness (68.64 µm), while 8 A yielded a uniform TiO₂ layer (∼41 µm) with optimal oxidation. Electrochemical tests further verified superior corrosion resistance at 8 A, with icorr as low as 4.08 × 10⁻¹ ⁰ A/cm² in 3.5 % NaCl, attributed to the formation of a dense and homogeneous oxide film. Higher currents (10–11 A) caused porosity and defects. The novelty of this work lies in employing 3D-printed Ti-6Al-4V electrodes, whose tailored internal architecture enhances spark stability and coating reproducibility capabilities not achievable with conventional or wrought electrodes. These findings establish an eco-efficient and effective approach for producing high-quality, corrosion-resistant titanium dioxide (TiO₂) coatings on stainless steel.