Carbonaceous minerals as corrosion products on the surface of bottles

During the corrosion process, as the ion exchange between the surface of the glass and the water progresses, the chemical structure of the surface changes and different structural layers are formed. These layers are characterised by various analytical techniques such as EPMA, XRD, FT-IR, TG-DTA and ICP-OES. Three carbonate mineral species namely calcite (CaCO3), shortite (Na2Ca2(CO3)3) and nyerereite (Na2Ca(CO3)2) have been identified at the outermost deposition layer. Critical parameters that affect the formation of the alkali depleted and silica enriched gel layer are investigated using some special test methods. Methylene blue solution reacts with the silanol groups of gel layer leaving a blue tint behind, the intensity of which varies with the extent of corrosion as the amount of silanol groups outcropped due to the increase of the porous structure area. A colour scale is developed to determine the level of corrosion and the results are correlated with the results of other known chemical analysis methods. The effect of annealing conditions on the chemical resistance of the surfaces and the role of the shape of the bottles on the water condensation at humid atmosphere are studied. The results of acid treatment and re-annealing of the corroded surfaces are described.