9Ni钢是制作液化天然气（LNG）储罐的主要材料。通过电化学法、挂片浸泡法、慢应变速率试验，研究了9Ni钢在模拟海水试压环境中及阴极保护条件下的腐蚀行为。结果表明：阴极保护电位（以下简称阴保电位）为-0.70~-1.00 V（相对于SCE，下同）时，9Ni钢的腐蚀速率由0.235 5 mm/a降至0.022 0~0.004 4 mm/a，保护度均在90%以上；在试压沉降周期内，-0.70 V阴保电位能够满足9Ni钢的耐缝隙腐蚀要求。阴保电位为-0.85~-0.93 V时，9Ni钢主要为韧性断裂，但-0.93 V时断口附近出现大量微裂纹；阴保电位为-0.95 V时，断口出现准解理特征，9Ni钢进入氢脆危险区。因此，为充分保证9Ni钢服役安全，LNG储罐在海水试压过程中，9Ni钢的阴保电位推荐值为-0.70~-0.90 V。

9Ni steel is the main material for liquefied natural gas (LNG) storage tents. The corrosion behavior of 9Ni steel in simulated environment of hydrostatic test using seawater and under the condition of cathodic protection was investigated by means of electrochemical method, immersion method and slow strain rate test (SSRT) method. The results showed that when the cathodic protection potential decreased in the rage of -0.70 V (vs. SCE the same below) ~ -1.00 V, the corrosion rate of 9Ni steel decreased from 0.235 5 mm/a to 0.022 0 ~ 0.004 4 mm/a, and the protection degrees all reached above 90%. Also, -0.70 V was able to meet the requirements of crevice corrosion resistance of 9Ni steel during the period of hydrostatic test. When the potential decreased in the range of -0.85 V ~ -0.93 V, 9Ni steel was mainly subject to ductile fracture. A large number of microcracks appeared near the fracture surface. Quasi-cleavage feature was found on the fracture surface at -0.95 V and 9Ni steel entered dangerous zone of hydrogen embrittlement. So in order to ensure the service safety of 9Ni steel, the recommended cathodic protection potential range of 9Ni steel was -0.70 V ~ -0.90 V during hydrostatic test using seawater of LNG storage tanks.