Effect of colloidal silica contents in the organic-inorganic hybrid coatings on the physical properties of the film on the metal surface

The coatings composed of colloidal silica, methyltrimethoxy silane (MTMS), water, and acid catalysts have been prepared with variation of colloidal silica contents from 0 to 20%. All the coatings were prepared and coated on the aluminum plate under the same condition except the contents of colloidal silica, and the compensating contents of MTMS and water with fixed molar ratio of MTMS and water to be 3. The physical properties were compared in terms of hardness, adhesion strength, corrosion, wear resistance, and thermo gravimetry analysis, etc. The pencil hardness was drastically increased with the addition of 5% colloidal silica particles and was further increased slightly by increase of additional silica. The corrosion resistance of the coating film against alkali solution was improved by increasing colloidal silica content, however, the acid resistance was less affected by the content of colloidal silica.