As-deposited sol-gel made TiO2-SiO2 films as protective coatings for silver

Silver surface is prone for tarnish when exposed to sulfide and sulfate environments. Present work reports protection of silver surfaces with sol-gel derived mixed oxides of titanium-silicon (TiO2-SiO2) thin films prepared at room temperature (300K) by dip coating technique without any post annealing. 0.1M and 0.3M titania and silica individual sols are mixed in fixed volume to prepare 0.1M (TS1) and 0.3M (TS3) titania-silica mixed oxides. The corrosion measurements of the coated and un-coated silver surfaces have been evaluated by conventional electro-chemical measurements; alkaline Na2S and Na2SO4 are the electrolytes. The corrosion rates have been estimated from Tafel plots. The titania-silica protective thin films have shown significant decrease in the corrosion rates: bare silver from 1.06mmpy to protected silver surface 0.07mmpy. Ti-O-Si covalent bonds are revealed in Raman spectra of the mixed oxide films. The present investigation shows that sol-gel derived titania-silica films protect the silver surface from alkaline sulfide and sulfate environment very effectively.