Pressure elements should be designed to minimize corrosion. Unless the process fluid requires better corrosion resistance, pressure elements should be 316 stainless steel (316 SS). For salt water or services where chloride stress corrosion is possible, pressure elements should be Monel. Pressure elements for instrument air or sweet water should be bronze. Most other process fluids require better corrosion resistance, for which 416 SS is usually acceptable. Consult a materials engineer regarding highly corrosive services. See API RP 551, Section 4.2.10.
