A self-healing corrosion protective coating was developed using TiO₂ particles and casein as pH-sensitive organic agents that is also environmentally friendly materials. A film structured of TiO₂ particles was formed on a substrate (magnesium alloy) by dip-coating followed by immersion in a casein solution. Casein was inserted and fixed in the particle film by changing the pH of the casein solution. The polarization resistance of the scratched specimen prepared by changing the pH of the solution from 12 to 5 increased with testing time, and a deposited film consisting of TiO₂ particles and casein was observed after the test.