Application of Taguchi design for optimization of corrosion behavior of amorphous silica thin film deposited through sol-gel dipping technique

Amorphous silica thin films were applied on the 316L stainless steel substrates by sol-gel dipping technique. The starting chemicals (TEOS, ethanol, HCl, PEG, and NaOH) were used to prepare a gel and then deposited on a substrate. The microstructure, topography, corrosion behavior, and surface hardness were investigated using SEM, AFM, electrochemical method, and micro-hardness measurements. The fabrication parameters utilized to enhance the anticorrosion and mechanical properties including calcinations temperature, pH value, and mole ratio of alkoxide to alcohol were studied. Taguchi approach was used as a statistical experimental design technique to set the optimal parameters. Roughness and current corrosion density were evaluated as the response parameter.
pH is the parameter of most major effect on the roughness; pH less than or equal to 4 increases the roughness but more pH value decreases the roughness. The ratio of alkoxide to alcohol is the most influential variable on current corrosion density. The increase of alkoxide amount improves the corrosion behavior, which might be related to the increase of the coating density. Consequently, the optimized conditions obtained through Taguchi method target at reaching the highest anticorrosion efficiency involving calcination at 300 °C, pH=6, and the mole ratio of alkoxide to alcohol as 0.167.