关键词: 热轧钢板；汽车腐蚀试验；湿度；腐蚀行为

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