a Department of Mechanical Engineering, K.S. Rangasamy College of Technology,

Tiruchengode -637215, Tamil Nadu, India.

b Department of Mechanical Engineering, Excel Engineering College, Komarapalayam,

Nammakal -637303, TamilNadu, India..

^cDepartment of Agricultural Engineering, Kongunadu College of Engineering and Technology, Thottiam, Trichy -621215, Tamil Nadu, India.

^dDepartment of Aeronautical Engineering, Excel Engineering College, Komarapalayam,

Nammakal -637303, TamilNadu, India.

Corrosion-induced material degradation is a critical global issue, causing annual economic losses and compromising the safety, performance, and service life of metallic infrastructure. Conventional protective coatings often degrade under aggressive service conditions, highlighting the need for multifunctional, environmentally benign corrosion inhibitors. In this study, barium titanate (BaTiO3), a ferroelectric perovskite oxide with high dielectric constant, chemical stability, and strong barrier-forming capability, was synthesised via a hydrothermal route to yield phase-pure, highly crystalline nanoparticles with an average crystalline and particle size of 27.81 nm and d50 = 47.93 nm. BaTiO3 coatings, applied via doctor- blade technique, were tested on copper, zinc, and mild steel (MS) substrates employing electrochemical impedance spectroscopy (EIS) and Tafel polarisation in 3.5% NaCl and acidic/alkaline media. In NaCl solution, inhibition efficiencies reached 88.74% (Cu), 86.92% (Zn), and 76.25% (MS), with positive Ecorr shifts and significant icorr reductions. In 1 M KOH, the efficiency for MS was 77.7%, while in 1 M HCl it was 48.82%, indicating better stability in alkaline media. To address reduced protection in acidic conditions, coating optimisation was performed by varying BaTiO₃ nanoparticle loadings (25, 50, 75, 100 mg). The 50 mg loading achieved the best performance in 2 M HCl, with Rp = 572.48 Ω·cm2, η = 85. 14%, and compact, defect-minimised surface coverage. Higher loadings led to coating heterogeneity, microcracks, and reduced inhibition, while lower loadings gave incomplete coverage. The optimisation strategy identified the nanoparticle concentration that maximises barrier integrity, dielectric shielding, and adhesion, establishing BaTiO3 as a promising eco-friendly corrosion inhibitor for chloride-rich and industrial environments.