Acid resistance
With acid resistance , the property of a solid (such as a metal hereinafter), even at high temperatures, no compounds with an acid to respond or even be dissolved. Materials such as glass or polytetrafluoroethylene as well as all precious metals and some passivation metals are resistant to many acids. Almost all metals dissolve in aqua regia , metals and even glass in hydrofluoric acid .
Metals and semi-metals
Metals are either acid-resistant because they
- as noble metals have a more positive normal potential than hydrogen or
- because they form a protective coating (usually an oxide ) against the reaction with acids , which, in contrast to pure metal, is resistant to acids ( passivation ). Examples are chrome , aluminum , titanium , lead , zinc . This property of chrome is used in chrome plating .
The semimetal silicon is also passivated by the formation of an oxide coating .
links
Some compounds are acid-resistant because they are thermodynamically extremely stable and therefore do not react with acids. Some polyhalogenated hydrocarbons such as polytetrafluoroethylene ( Teflon ) are resistant to acids, but they decompose at high temperatures. Teflon is used as a coating similar to chrome, but it is elastic. The best known acid-resistant compound is glass. This material property is based on the high stability of the main component silicon dioxide. Only hydrofluoric acid dissolves glass.
literature
- Otto Lange: Metals and Minerals . Springer, Berlin Heidelberg 1923.
- Eberhard Roos, Karl Maile: Materials science for engineers . Springer, Heidelberg 2011, ISBN 978-3-642-17463-6 .
Web links
- Chemical resistance (accessed April 1, 2016)
- PH - X Supra 1.2892 highest rust and acid resistance (accessed April 1, 2016)
- Acid resistance (accessed April 1, 2016)