Mechanism of formation of silica-silicate thin films on zinc

The formation of silica-silicate thin films on zinc from a colloidal solution (or sol) of silica was studied using a microbalance. Thin films were made by immersion of zinc foil in a sol composed of colloidal silica particles and sodium silicate. The rest potential and weight gain were recorded simultaneously and correlated with pH changes at the zinc surface measured with a flat-bottomed pH electrode. The effect of the composition, pH, and agitation of the silica sol on the deposition process was thoroughly studied. The various factors governing the deposition were discussed leading to a phenomenological model of the thin-film deposition.