Pit depth statistics. (unit: mm).

The C01 type diaphragm coupling demonstrates effective performance in high-concentration seawater salt fog environments. However, the fastener material for this coupling must possess high mechanical properties and strong resistance to seawater corrosion. This study evaluates the suitability of 17−4 precipitation hardening (PH) stainless steel for diaphragm coupling fasteners through a series of tests, including pitting corrosion, crevice corrosion, stress corrosion, fatigue, galvanic corrosion, and cyclic immersion. The results show that the weight loss of 17−4PH stainless steel sample is 13.71% after pitting test and 7.73% after crevice test. However, after stress corrosion, fatigue, and galvanic corrosion tests, the 17−4PH stainless steel sample exhibits minimal corrosion sensitivity. These findings indicate that 17−4PH stainless steel is particularly susceptible to crevice and pitting corrosion. Consequently, 17−4PH shows no pronounced corrosion sensitivity within 15 days of exposure, supporting its provisional use in marine couplings subject to short-term salt fog environments, with caution regarding crevice corrosion risks. 17−4PH is suitable for marine coupling fasteners when combined with passivation, crevice sealing, or design optimization to mitigate pitting and crevice corrosion. Overall, this study provides an experimental basis for the application of 17−4PH stainless steel in diaphragm couplings under high salt fog environments.

C01型膜片联轴器（diaphragm coupling）在高浓度海水盐雾环境中展现出优异的使用性能。但该联轴器的紧固件材料需具备高力学性能与极强的海水腐蚀抗性。本研究通过点蚀、缝隙腐蚀、应力腐蚀、疲劳、电偶腐蚀以及循环浸泡等一系列试验，评估了17-4沉淀硬化（precipitation hardening, PH）不锈钢用于膜片联轴器紧固件的适配性。试验结果显示，17-4PH不锈钢试样在点蚀试验后的质量损失率为13.71%，缝隙腐蚀试验后为7.73%。不过经应力腐蚀、疲劳及电偶腐蚀试验后，该试样仅表现出极微弱的腐蚀敏感性。上述研究结果表明，17-4PH不锈钢对缝隙腐蚀与点蚀尤为敏感。但在暴露15天的周期内，17-4PH未表现出显著的腐蚀敏感性，这支持其可临时应用于短期盐雾环境下的船用联轴器，但需警惕缝隙腐蚀风险。若配合钝化处理、缝隙密封或设计优化以缓解点蚀与缝隙腐蚀问题，17-4PH可适用于船用联轴器紧固件。本研究整体为17-4PH不锈钢在高盐雾环境下的膜片联轴器应用提供了实验依据。