A number of elastomers possess good resistance when exposed to dilute acids at room temperature.
These materials include AFLAS®, Butyl, Epichlorohydrin, Ethylene Propylene, Fluorocarbon, Fluorosilicone, Perfluoroelastomer, Natural Rubber, Chloroprene (Neoprene) Nitrile, and Teflon™.
The acid resistance of these compounds, however, significantly lessens with both increasing acid concentrations and rising temperatures.
Best Choices
- As temperatures and concentrations of nitric and hydrochloric acids rise, perfluoroelastomers such as Kalrez or Chemraz have demonstrated good performance in lab tests.
- As temperatures rise above 158°F, only the chemical inertness of Teflon™ can be relied upon for maintenance of a seal exposed to hydrochloric or nitric acids.
Note: Teflon™ has been laboratory tested (by DuPont) for 168 hours of exposure to 37% hydro-chloric acid, at 248°F, with only 0.03% of observed weight gain. It has further been tested for 12 months of exposure to 10% nitric acid, at 158°F, with 0.1% weight gain. Teflon™ has also been shown by DuPont to undergo only slow oxidative attack by 70% nitric acid, under pressure, at 480°F.