Abstract: This paper studies the effect of humidity variation on the corrosion rate of hot-rolled steel sheets under automotive corrosion test conditions. The micromorphology and phase composition of the corroded surface are analyzed by scanning electron microscope and X-ray diffractometer. The results show that alternating humidity exerts a greater influence on the corrosion rate of hot-rolled steel sheets than continuous high humidity, while the two conditions present a basically consistent trend of corrosion rate change. In the initial acceleration stage within the first 5 days of the test, the corrosion rate of the steel sheet increases continuously, cracks appear on the rust layer surface and Fe2O3 is formed. During 5 to 7 days, the corrosion rate decreases significantly, surface cracks of the rust layer reduce, and Fe2O3 and corrosion-resistant α-FeOOH are generated. At 20 days, the corrosion rate rises continuously with obvious spalling of the rust layer, and the corrosion products mainly include Fe3O4, Fe2O3 and a small amount of α-FeOOH. Alternating humidity significantly promotes the later corrosion development of hot-rolled steel sheets, which provides a reference for the anti-corrosion design of hot-rolled steel sheets for automobiles.

Key words: hot-rolled steel plate; automobile corrosion test; humidity; corrosive behavior

摘要： 研究汽车腐蚀试验工况下湿度变化对热轧钢板腐蚀速率的影响，采用扫描电子显微镜、 X 射线衍射仪分析腐蚀面微观形貌与物相组成。结果表明，交变湿度对热轧钢板腐蚀速率的 影响大于持续高湿环境，二者腐蚀速率变化趋势基本一致。试验前 5 天为腐蚀加速初期，钢 板腐蚀速率持续上升，锈层表面出现裂纹并生成 Fe2O3；5 至 7 天时腐蚀速率显著下降，锈层 表面裂纹减少，生成 Fe2O3 与具有一定耐蚀性的 α-FeOOH；至 20 天时腐蚀速率再次上升，锈 层发生明显剥落，腐蚀产物主要为 Fe3O4、Fe2O3 及微量 α-FeOOH。湿度交变条件可显著促进 热轧钢板后期腐蚀发展，对汽车用热轧钢板防腐设计具有参考意义。

关键词: 热轧钢板；汽车腐蚀试验；湿度；腐蚀行为