Formation of SiO2 Protective Coating on SUS 304 Stainless Steel by Chemical Vapor Deposition using TEOS-O3 Gas System
Shuji Kikkawa, Tetsu Go, Nobuyoshi Hara, Katsuhisa Sugimoto
SiO2 films were formed on SUS 304 stainless steels by CVD using TEOS-O3 gas system. Changes in the deposition rate, composition, and refractive index of the films were investigated as a function of substrate temperature. Influences of substrate temperature and film thickness on corrosion resistance of the steels coated with SiO2 films were examined by measuring activation time and anodic polarization curve in 1kmol·m-3 HCl. The deposition rate increased with increasing substrate temperature up to 573K, whereas it decreased above 573K. The amount of Si-OH bonds in films decreased with increasing substrate temperature and the bonds hardly existed at temperatures above 573K. The refractive index of the films increased with increasing substrate temperature up to 573K, and then it stayed at a constant value of 1.45 up to 673K. The activation time increased and the critical passivation current decreased with increasing thickness of SiO2 films. The increase in the activation time and the decrease in the critical passivation current were more remarkable in the case of higher film forming temperature. Therefore, the corrosion resistance of SiO2-coated SUS 304 stainless steels increases with increasing thickness and formation temperature of the SiO2 films.