Abstract: The C01 type diaphragm coupling is exposed to high concentrations of seawater salt spray for a long time during operation. The fastener material of the coupling should not only have high mechanical properties, but also have strong resistance to seawater salt spray corrosion. The feasibility of using 15-5PH (0Cr15Ni5Cu4Nb) stainless steel material for diaphragm coupling fasteners was tested through tests such as pitting corrosion, crevice corrosion, stress corrosion, fatigue corrosion, and galvanic corrosion. The results indicate that 15-5PH stainless steel exhibited significant crevice corrosion and slight pitting corrosion, but had no stress corrosion or fatigue corrosion sensigbility. When coupled with TC4 titanium alloy, 15-5PH stainless steel had no electrochemical corrosion. 15-5PH stainless steel could be used as a fastener for TC4 titanium alloy membrane discs in open marine environments. But attention should be paid to avoiding the occurrence of crevice corrosion.