PEEK also exhibits good chemical resistance in many environments, including alkalis (i.e. sodium, potassium and ammonium hydroxides), aromatic hydrocarbons, alcohols (i.e. ethanol, propanol), greases, oils and halegonated hydrocarbons.
However, its performance in acids is very dependent on the type of acid - PEEK shows poor resistance in concentrated [[sulphiricsulfuric acid|sulfuric]], [[nitric acid|nitric]], [[hydrochloric acid|hydrochloric]], [[hydrobromic acid|hydrobromic]] and other mineral acids (though performance may be adequate for short term use with these acids in very dilute form). Its resistance to [[hydrofluoric acid]] and [[oleum]] is very poor. PEEK shows good resistance to [[phosphoric acid]] and organic acids (acetic, citric, oxalic, tataric etc.), but varying resistance in the presence of halogens. PEEK is resistant to dissolution by some formaldehydes and ketones such as acetone, but not (at higher temperature) methylethyl ketone.
