通过干湿循环测试、SEM、TEM、XRD和电化学方法研究了一种9%Cr合金钢在含Cl^-环境中的初期腐蚀行为，探讨了复合夹杂物(Mg, Si, Al)O-MnS和富Cr的M₂₃C₆对其局部腐蚀行为的影响。结果表明，合金钢初期耐蚀性能较09CuPCrNi提高了12倍以上，在360 h的干湿循环过程中发生局部腐蚀，锈层下的蚀坑深度符合Lognormal分布，蚀坑的最大深度(D_max)与平均深度(D_ave)随时间(t)变化规律分别符合幂函数D_max = 8.4844 × t ^0.65717和D_ave = 7.3181 × t ^0.53866。合金钢锈层的致密度和α / γ^* (α-FeOOH / (γ-FeOOH + Fe₃O₄ + β-FeOOH)含量比)随腐蚀时间延长均不断增加，但高Cr的添加推迟了腐蚀进程，使得锈层未完整覆盖表面，仅提供了有限的保护能力，因而根据幂函数拟合失重数据得到的指数大于1。复合夹杂物(Mg, Si, Al)O-MnS通过MnS或单一MgO区域的局部优先溶解导致亚稳态点蚀，但其在2%NaCl溶液中浸泡300 min并未诱发周围基体溶解，而富Cr的M₂₃C₆析出导致基体的Cr消耗是优先诱发局部腐蚀的主要原因。

The South China Sea is a marine atmosphere environment with high humidity, high salt content, and strong radiation. Traditional weathering steel and 3Ni advanced weathering steel cannot meet the service requirements in the South China Sea environment, necessitating the development of steel with improved corrosion resistance. Alloy steels with Cr of 2.5%-10% (mass fraction) provide a marginal gain in corrosion performance at a low cost and have great potential for marine atmospheric application. A 9%Cr alloy steel was designed to obtain higher corrosion resistance, and the relevant results can offer a reference for developing novel corrosion-resistant steels for the marine atmospheric environment. The initial corrosion behavior of 9%Cr alloy steel in a Cl^- containing environment was investigated using dry-wet cycle test, SEM, TEM, XRD, and electrochemical approaches, and the effects of composite inclusions (Mg, Si, Al)O-MnS and Cr-rich M₂₃C₆ on its local corrosion behavior were discussed. The findings demonstrate that the initial corrosion resistance of alloy steel was more than 12 times that of 09CuPCrNi, and local corrosion occurred during the 360-h dry-wet cycle. Pits' depth below the rust layer followed the lognormal distribution, and the pits' maximum depth (D_max) and average depth (D_ave) with time (t) were in line with the power functions D_max = 8.4844 × t ^0.65717 and D_ave = 7.3181 × t ^0.53866, respectively. The rust layer's compactness and the α / γ^* ratio increased over time, but the addition of high Cr delayed the corrosion. Thus, the rust layer did not entirely cover the surface and only provided limited protection, and an exponent value obtained by fitting the weight loss according to the power function was greater than 1. (Mg, Si, Al)O-MnS caused metastable pitting corrosion through a preferential dissolution of MnS or MgO regions, but its immersion in 2%NaCl solution for 300 min did not induce surrounding matrix's dissolution. The Cr consumption caused by Cr-rich M₂₃C₆'s precipitation was the primary reason for preferentially inducing local corrosion.