An infrared spectroscopic study of sodium silicate adsorption on porous anodic alumina

Sodium silicate solutions, also known as ‘water-glass’, are used for a wide variety of applications. In particular, they are commonly used in pre-treatments of aluminum alloys as cleaners and corrosion inhibitors. Silicate films are known to be promising for corrosion protection and to confer high hydrophilicity. One of the main issues in the study of the formation of silicate films on metal oxides is the complexity of the anionic speciation in aqueous solution. In this work, the mechanism of sodium silicate interaction with porous anodic alumina and its dependence on the solution characteristics is studied by means of Fourier transformed infrared spectroscopy (FTIR). Grazing angle-FTIR and attenuated total reflection-FTIR are used in order to monitor the chemical changes occurring with time on the surface upon silicate adsorption. The effect of the SiO2/Na2O molar ratio and the temperature is studied. The role of rinsing is investigated when the alumina surface is washed in water after the silicate treatment. A chemical description of the phenomena occurring during silicate treatment is given.

Publication year:2013

Keywords:silicate, alumina