Glass corrosion

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Glass corrosion on an old Roman bottle

As glass corrosion , glass corrosion , glass fire , Glaspest or glass disease which is structural change and associated weathering of the surface of glass by various chemical and physical influences referred.

description

Glasses affected by glass corrosion show in the case of transparent objects a cloudiness, which is caused by microscopic roughening of the surface. Glasses that have been in the ground for decades or centuries have a typically dirty, rainbow-colored surface.

Explanation

Influence of the addition of selected glass components on the chemical resistance of a given base glass to corrosion by water (corrosion test ISO 719)

Glass corrosion begins with the dissolving out of oxides of various elements , such as sodium , potassium , calcium , barium or boron . The physical properties of the material change in the affected areas. A gel layer forms , which reacts with ions of the active substance to form a hazy coating. This affects the transparency of the surface and leads to microscopic cracks.

Influence of the glass composition

Corrosion can be reduced by adding certain oxides during glass production. Commonly used are aluminum oxide , zirconium oxide , moderate concentrations of boron trioxide (see borosilicate glass) or high concentrations of silicon dioxide . Too high a boron oxide content reduces the resistance to corrosion. Special phosphate or borosilicate glasses corrode very strongly due to phase separation phenomena in the glass, which is used technically in the Vycor process.

Influence of the acting substance

Glass fire caused by dishwasher detergent

In an acid medium , an exchange of place cations from the glass surface against of oxonium ions originating protons instead. If the resulting salts are washed away (excess water), a gel layer is created on the glass, which slows down further corrosion. In the event of a water deficit, salts are formed which are deposited on the glass. The same exchange of cations for hydrogen ions takes place in a neutral environment, but the leached cations lead to an alkalization of the environment. In an alkaline environment, components of the glass network (SiO - ) are exchanged for OH groups , which means that the glass network is broken down. In the event of a water deficit, this process accelerates. The transport and storage of glasses should therefore take place in a slightly acidic environment.

A low pH value and low salt content of the liquid and a high temperature accelerate the corrosion compared to that in a slightly acidic environment. For example, softer water in the dishwasher or acid rain in glass windows causes a higher dissolution of minerals from the surface. Accordingly, there are various standardized methods for quantifying glass corrosion, including tests to determine the chemical resistance of glass to water ( DIN 12111 or ISO 719 with division into hydrolytic classes ), acids (DIN 12116), bases (DIN 52322 or ISO 695) and weather conditions.

Examples

  • In 1993, the Würzburg Fraunhofer Institute for Silicate Research carried out a literature study on the corrosion mechanisms of historical glass windows . The researchers discovered that window glass from the 11th to 16th centuries has a low chemical resistance to environmental influences due to the high proportions of potassium and calcium oxide . A silicon dioxide content below 66 percent increases susceptibility to weathering. To protect against further destruction of architectural monuments made of glass, a corrosion protection system based on organically modified silicates was developed, the so-called ORMOCER .
  • In 2001 the Verband Deutscher Glasbläser e. V. on the destruction of a glass pipe in a chemical plant. Here, the slow corrosion of the glass material caused by hydrochloric acid flowing through it, together with abrasive glass particles contained in the solution, destroyed the line.

Others

Dishwashing detergent manufacturers like to use the terms glass rust and glass corrosion to describe supposedly improved new substances in their products. In fact, glass corrosion in the dishwasher depends primarily on the quality of the glass material used. Furthermore, damage is often caused by purely mechanical effects, such as rubbing glasses against one another or contact with parts of the dishwasher.

Similar phenomena

Individual evidence

  1. ↑ Glassproperties.com Calculation of the Chemical Durability (hydrolytic class, Corrosion) of Glasses
  2. ↑ Hans Joachim Gläser: Thin film technology on flat glass, Karl Hofmann, Schorndorf 1999
  3. ↑ Werner Vogel : Glaschemie , Springer 1992
  4. ↑ a b Stiftung Warentest : glasses and cutlery in the dishwasher ( test 02/2004)
  5. ↑ Fraunhofer Institute for Silicate Research: Corrosion Mechanisms of Historic Glass Windows (1993) ( Memento from July 19, 2012 in the web archive archive.today )
  6. ↑ Fraunhofer Institute for Silicate Research: Glass Preservation (1993) ( Memento from September 5, 2012 in the web archive archive.today )
  7. ↑ Fraunhofer Institute for Silicate Research: ORMOCERe / Hybrid Polymers
  8. ^ Association of German Glass Blowers eV: Unexpected damage to a glass pipeline (2001) ( Memento from December 26, 2012 in the Internet Archive )
  9. ↑ Telering.de: Dishwasher advice: Glaskorrosion ( Memento from September 28, 2007 in the Internet Archive )
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