Uses

<h3 >Oil refining</h3>

In a standard <a href="http://en.wikipedia.org/wiki/Oil_refinery" title="Oil refinery" >oil refinery</a> process known as <a href="http://en.wikipedia.org/wiki/Alkylation" title="Alkylation" >alkylation</a>, <a href="http://en.wikipedia.org/wiki/Isobutane" title="Isobutane" >isobutane</a> is alkylated with low-molecular-weight<a href="http://en.wikipedia.org/wiki/Alkene" title="Alkene" >alkenes</a> (primarily a mixture of <a href="http://en.wikipedia.org/wiki/Propylene" title="Propylene" class="mw-redirect" >propylene</a> and <a href="http://en.wikipedia.org/wiki/Butylene" title="Butylene" >butylene</a>) in the presence of the strong acid <a href="http://en.wikipedia.org/wiki/Catalyst" title="Catalyst" class="mw-redirect" >catalyst</a> derived from hydrofluoric acid. The catalyst protonates the alkenes (propylene, butylene) to produce reactive<a href="http://en.wikipedia.org/wiki/Carbocation" title="Carbocation" >carbocations</a>, which alkylate isobutane. The reaction is carried out at mild temperatures (0 and 30 °C) in a two-phase reaction.

<h3 >[<a href="http://en.wikipedia.org/w/index.php?title=Hydrofluoric_acid&action=edit&section=5" title="Edit section: Production of organofluorine compounds" >edit</a>]Production of organofluorine compounds</h3>

The principal use of hydrofluoric acid is in <a href="http://en.wikipedia.org/wiki/Organofluorine_chemistry" title="Organofluorine chemistry" >organofluorine chemistry</a>. Many <a href="http://en.wikipedia.org/wiki/Organofluorine_compounds" title="Organofluorine compounds" class="mw-redirect" >organofluorine compounds</a> are prepared using HF as the fluorine source, including <a href="http://en.wikipedia.org/wiki/Polytetrafluoroethylene" title="Polytetrafluoroethylene" >Teflon</a>, <a href="http://en.wikipedia.org/wiki/Fluoropolymer" title="Fluoropolymer" >fluoropolymers</a>, <a href="http://en.wikipedia.org/wiki/Fluorocarbon" title="Fluorocarbon" >fluorocarbons</a>, and <a href="http://en.wikipedia.org/wiki/Refrigeration" title="Refrigeration" >refrigerants</a>such as <a href="http://en.wikipedia.org/wiki/Freon" title="Freon" class="mw-redirect" >freon</a>.<a href="http://en.wikipedia.org/wiki/Hydrofluoric_acid#cite_note-Ullmann-2" >[3]</a>

<h3 >[<a href="http://en.wikipedia.org/w/index.php?title=Hydrofluoric_acid&action=edit&section=6" title="Edit section: Production of fluorides" >edit</a>]Production of fluorides</h3>

Most high-volume inorganic fluoride compounds are prepared from hydrofluoric acid. Foremost are Na3AlF6,<a href="http://en.wikipedia.org/wiki/Cryolite" title="Cryolite" >cryolite</a>, and AlF3, <a href="http://en.wikipedia.org/wiki/Aluminium_trifluoride" title="Aluminium trifluoride" class="mw-redirect" >aluminium trifluoride</a>. A molten mixture of these solids serves as a high-temperature solvent for the production of metallic <a href="http://en.wikipedia.org/wiki/Aluminium" title="Aluminium" >aluminium</a>. Given concerns about fluorides in the environment, alternative technologies are being sought. Other inorganic fluorides prepared from hydrofluoric acid include <a href="http://en.wikipedia.org/wiki/Sodium_fluoride" title="Sodium fluoride" >sodium fluoride</a> and <a href="http://en.wikipedia.org/wiki/Uranium_hexafluoride" title="Uranium hexafluoride" >uranium hexafluoride</a>.<a href="http://en.wikipedia.org/wiki/Hydrofluoric_acid#cite_note-Ullmann-2" >[3]</a>

<h3 >[<a href="http://en.wikipedia.org/w/index.php?title=Hydrofluoric_acid&action=edit&section=7" title="Edit section: Etchant and cleaning agent" >edit</a>]Etchant and cleaning agent</h3>

The ability of hydrofluoric acid to dissolve metal oxides is the basis of several applications. It removes oxide impurities from <a href="http://en.wikipedia.org/wiki/Stainless_steel" title="Stainless steel" >stainless steel</a>, a process called pickling, and <a href="http://en.wikipedia.org/wiki/Silicon" title="Silicon" >silicon</a> wafers in the <a href="http://en.wikipedia.org/wiki/Semiconductor" title="Semiconductor" >semiconductor</a> industry. In this regard it is also referred to as BHF, (when Buffered with Ammonium Fluoride), and BOE (for Buffered Oxide Etch). It is a significant constituent of <a href="http://en.wikipedia.org/wiki/Wright_Etch" title="Wright Etch" class="mw-redirect" >Wright Etch</a> and the similar HNA (HF+Nitric+Acetic Acid) etch. In similar manner, it is also used to etch <a href="http://en.wikipedia.org/wiki/Glass" title="Glass" >glass</a>. A 5% to 9% hydrofluoric acid gel is also commonly used to etch all ceramic dental restorations to improve bonding.<a href="http://en.wikipedia.org/wiki/Hydrofluoric_acid#cite_note-4" >[5]</a> For similar reasons, dilute hydrofluoric acid is a component of household rust stain remover and in <a href="http://en.wikipedia.org/wiki/Car_wash" title="Car wash" >car washes</a> in "wheel cleaner" compounds.<a href="http://en.wikipedia.org/wiki/Hydrofluoric_acid#cite_note-5" >[6]</a> Hydrofluoric acid attacks glass by reaction with silicon dioxide to form gaseous or water-soluble silicon fluorides. This dissolution process proceeds as follows:

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Because of its ability to dissolve iron oxides as well as silica-based contaminants, hydrofluoric acid is used in pre-commissioning boilers that produce high-pressure steam.

<h3 >[<a href="http://en.wikipedia.org/w/index.php?title=Hydrofluoric_acid&action=edit&section=8" title="Edit section: Niche applications" >edit</a>]Niche applications</h3>

Because of its ability to dissolve oxides, hydrofluoric acid is useful for dissolving rock samples (usually powdered) prior to analysis. In similar manner, this acid is used in <a href="http://en.wikipedia.org/wiki/Acid_maceration" title="Acid maceration" >acid macerations</a> to extract organic fossils from silicate rocks. Fossiliferous rock may be immersed directly into the acid, or a cellulose nitrate film may be applied (dissolved in amyl acetate), which adheres to the organic component and allows the rock to be dissolved around it.<a href="http://en.wikipedia.org/wiki/Hydrofluoric_acid#cite_note-Edwards1982-6" >[7]</a>

Diluted hydrofluoric acid (1 to 3 %wt.) is used in the <a href="http://en.wikipedia.org/wiki/Petroleum_industry" title="Petroleum industry" >petroleum industry</a> in a mixture with other acids (HCl or organic acids) in order to stimulate the production of water, oil, and gas wells specifically where sandstone is involved.[<a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed" >citation needed</a>]

Hydrofluoric acid is also used by some collectors of antique glass bottles to remove so-called 'sickness' from the glass, caused by acids (usually in the soil the bottle was buried in) attacking the soda content of the glass.[<a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed" >citation needed</a>]