Chemical Resistance & Valve Compatibility Guide

An A rating indicates excellent chemical resistance — no measurable effect on the material under standard conditions (ambient temperature, full concentration). The material is recommended for continuous service with that chemical. In practice, an A-rated material shows no swelling, softening, loss of strength, or discoloration after prolonged exposure. A ratings are the most reliable but should still be verified at your actual operating temperature, since resistance can decrease significantly at elevated temperatures even for A-rated materials.

For metallic valve bodies, Hastelloy C-276 offers the broadest chemical resistance profile, covering most acids, alkalis, chloride environments, and oxidizing agents that attack standard stainless steels. For seats and seals, PTFE (polytetrafluoroethylene) is chemically inert to virtually all chemicals at ambient temperature. For extreme applications — fuming acids, fluorine service, or applications above PTFE's temperature limits — FFKM (perfluoroelastomer) offers the best elastomeric resistance. The "most resistant" material always depends on the specific chemical, concentration, temperature, and pressure of your service.

Temperature has a dramatic effect on chemical compatibility. Published ratings are almost always based on ambient temperature (70°F / 21°C). As temperature increases, the rate of chemical attack typically increases exponentially — a rough rule of thumb is that corrosion rate doubles for every 18°F (10°C) increase. Elastomers and thermoplastics are especially sensitive: an EPDM seal rated A for a dilute caustic at ambient may swell and fail at 180°F service. Always consult our engineers at 888-825-8800 for high-temperature chemical service applications.

No — brass is not compatible with sulfuric acid at most commercially relevant concentrations. Sulfuric acid attacks copper and zinc (the two base metals in brass), causing rapid dezincification and general corrosion. Brass valves will corrode, leak, and fail in sulfuric acid service. For dilute sulfuric acid (below ~10%), 316 stainless steel with PTFE seats and seals is a common choice. For concentrated sulfuric acid, Alloy 20 or high-silicon cast iron body valves with PTFE seats are typically specified. Always verify with our engineers for your exact concentration and temperature.

Hydrochloric acid (HCl) is one of the most aggressive chemicals for metallic valve materials. For body material, Hastelloy C-276 provides excellent resistance to all HCl concentrations at moderate temperatures. PVDF (Kynar) and CPVC thermoplastic body valves are economical alternatives for lower-pressure systems. Standard stainless steels (304, 316) are not suitable — HCl causes rapid pitting and stress corrosion cracking. For seats and seals, PTFE or FFKM are the preferred choices. The specific concentration and temperature of your HCl service significantly affects which materials are viable — use our tool above or call us at 888-825-8800.