Design of a Ti-Zr-P-Si Chromium-Free Passivation Composite Film with High Corrosion Resistance and Eco-Friendliness on Tinplate

Tinplate is widely used in food packaging because of its non-toxic and tasteless properties, but the conventional passivation treatment involving carcinogenic chromate poses significant risks to both human health and the environment. Nevertheless, achieving comparable performance indicators with existing chromium-free alternatives remains challenging. Herein, we developed a high corrosion resistant and eco-friendly Ti-Zr-P-Si chromium-free passivation film on tinplate by hybrid synergistic assembly between organosilicon oligomer and inorganic metal salt containing Ti⁴⁺ and Zr⁴⁺. Compared with traditional passivation films containing Cr, such chromium-free passivation film exhibited superior resistance to sulfur and acid and adhesive force, revealing that chromium-free passivation achieved Grade 1 in all categories. Moreover, electrochemical tests show that the AC impedance and corrosion rate of chromium-free passivation film are comparable to chromium passivation film. Importantly, the fabrication of this chromium-free passivation film employs a simple process and low cost, harmless elements and satisfies environmental necessities. This work is important for the advancement of eco-friendly and high-performance passivation processes in the tinplate industry.