By using LPD (Liquid Phase Deposition) method, SiO
2 thin film can be formed in H
2SiF
6 aqueous solution below 50°C. However, in almost all cases, thin films formed by LPD method were on glass substrate. Therefore, in this study, problems concerning the SiO
2 film formation process on SUS304 stainless steel substrate were examined by incorporating various electrochemical techniques. From the results of potential and current density measurements under coupling conditions with a Pt counter electrode, the importance of keeping SiO
2 supersaturated state of solution and the need of pretreatment and cathodic protection of stainless steel substrate were recognized for preventing the corrosion damage of substrate from the severe environment of H
2SiF
6 aqueous solution.
Then, the thin SiO
2 film formation process was examined through microscopic observations by SEM and chemical analysis by EPMA. As a result, the progress in the deposition process was recognized with time. However, some defects were recognized in the deposited thin SiO
2 film on SUS304 stainless steel substrate. These defects may strongly influence the corrosion resistance of SiO
2 thin film coated steel. On the other hand, some acceleration in the thin film formation process was recognized when the deposition was conducted under a cathodically protecting condition at which an aluminum piece was used as a sacrificial anode. It may be brought about by the acceleration in anodic dissolution of aluminun piece and also by the pH increase with H
2 gas generation in the electrochemical reaction.
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