Fluorine is chemical element with the atomic number 9 and belongs tot he group of halogens. In its pure form, it is a diatomic gas F2. However, fluorine does not occur in its pure form in nature but only in combination with other elements, usually in mineral form. Fluorine is an extremely reactive element, which means that it is highly toxic because it reacts extremely violently in the body and is therefore highly corrosive. On the other hand, many compounds with fluorine are therefore extremely stable and as a result practically do not react with other substances. This is evident for example from the practically complete insolubility of PTFE and other fluorine compounds, and the complete inertness of gases such as tetrafluormethane CF4 and sulphur hexafluoride SF6. Fluorine compounds are important substances in plasma technology: While the above-named substances are chemically practically inert, they do in fact react in the plasma by radical formation. im Plasma durchaus. UV radiation also breaks down C-F compounds.<br/>This generates fluorine radicals which make CF4 and SF6 particularly effective etching gases, particularly for silicon, generating silicon tetrafluoride SiF4. This makes it possible to separate fluorine radicals from PTFE, which react with the radicals in the hydrogen plasma to form hydrogen fluoride HF. Radicals remain at the PTFE which make it wettable and gluable. On the other hand, plasma polymerisation of fluorocarbons can create PTFE-like coats and thus ultra-hydrophobic and Epilam coats. Containers can be plasma-treated to receive fluoride coats which form barrier coats to prevent the permeation of various liquids such as petrol/gasoline.