Improvement of corrosion resistance of metals by an environmentally friendly silica coating method

Corrosion resistance of stainless steel and Zn plated steel can be improved by a chromium-free environmentally friendly chemical solution deposition method. Precursor solutions were prepared from tetraethoxysilane with polymer, and were deposited on stainless steel, Zn plated steel and aluminum alloy by dip coating, followed by heat treatment. Addition of polymer to the precursor solution proved very effective in preparing films free from cracks on stainless steel and aluminum alloy substrates. The corrosion resistance was greatly improved by the resulting sub-micron thick silica-polymer hybrid film coatings on stainless steel and on Zn plated steel prepared at 200°C. The hardness of aluminum alloy coated with silica-PMMA hybrid film was improved by 7% over uncoated alloy.