Attack on soda-lime-silica glass bottles by acetic, citric and oxalic acids

Abstract

The corrosion resistance of soda-lime-silica glass bottles toward the action of aqueous Solutions of citric, acetic and oxalic acids was studied and compared with that toward HCl and water. The corrosion resistance was tested by subjecting the internal surface of the bottles to the action of Solutions of different concentrations of the organic acids at 95 °C for periods in the ränge of 15 min to 6 h. The quantities of Na₂O and SiO₂ extracted from the bottles under the conditions of attack were taken as a measure of the resistance to corrosion. The results obtained indicated that the extraction of Na₂O by Solutions of low concentrations of the different acids and wate? can be arranged in the following order: H₂O > citric acid > acetic acid > HCl > oxalic acid. Such behaviour was found to follo\ the order of the solubility of the corresponding sodium salts formed with the aqueous Solutions rather than the proton availabilit: in these Solutions. The relative magnitude of dissolution of SiO₂ was found to follow another order: H₂O > HCl > oxalic acid > citric acid > aceti acid. The decreasing solubility of SiO₂ by the organic acids, in comparison with that by HCl or water, was attributed to the formatio; of Oxalate, citrate and acetate complexes with silica which cover the glass surface and retard further dissolution of silica. Differences between the various organic acids in the dissolution of Na₂O or SiO₂ were not observed by increasing their concer trations. This behaviour was attributed to the increase in the concentration of the organosilicon Compound formed which is adsorbe on the glass surface acting as an effective barrier to further dissolution of glass.