耐候钢和碳钢在竖直方向上的腐蚀行为

为研究耐候钢和碳钢在竖直方向上的腐蚀行为，利用干湿循环腐蚀试验，模拟研究了耐候钢和碳钢在表面受到雨水反复冲刷的条件下，竖直方向上不同位置的腐蚀行为特征以及锈层的形成和演变。结果表明，耐候钢试样和碳钢试样在干湿循环一定周期后，上部腐蚀程度较轻，底部腐蚀程度较重，而中部的腐蚀程度则随竖直方向位置的下移而明显加重；碳钢试样底部的腐蚀程度随腐蚀时间的延长而加重，但耐候钢试样底部的腐蚀至一定程度后几乎不再继续；碳钢试样锈层形貌随竖直方向位置的下移而逐渐粗化，锈层形态和致密度变化较小，耐候钢试样的锈层形貌则随竖直方向位置的下移而逐渐细化，锈层形态由球状变为块状，致密度明显增加，这也导致了耐候钢的锈层电阻明显高于碳钢的锈层电阻；在干湿循环过程中，湿润时间会影响腐蚀产物的类型，湿润时间较短时，腐蚀产物以β-FeOOH为主，随着湿润时间的延长，腐蚀产物逐渐向γ-FeOOH转变。

Corrosion behaviors of weathering steel and carbon steel in vertical direction

In order to study the corrosion behavior of weathering steel and carbon steel in vertical direction, the corrosion behavior characteristics and formation and evolution of rust layer for weathering steel and carbon steel at different positions in vertical direction were simulated and studied under the condition that surfaces of weathering steel and carbon steel were repeatedly washed by rainwater using the dry-wet cycle corrosion test. The results show that the corrosion degree of upper part in weathering steel specimen and the carbon steel specimen after a certain period of dry-wet cycle is lighter, the corrosion degree of the bottom part is heavier, while the corrosion degree of the middle part is increased obviously with the downward movement of vertical position. The corrosion degree of carbon steel specimen bottom increases with the prolongation of corrosion time, but the corrosion of weathering steel specimen bottom hardly continues after a certain degree of corrosion. The morphology of rust layer for carbon steel specimen coarsens with the downward movement of vertical position, and the morphology and density of rust layer have little change. The morphology of rust layer for weathering steel specimen is gradually refined with the downward movement of vertical position, the morphology of rust layer changes from spherical to block and the density increases significantly, which also leads to the rust resistance of weathering steel is significantly higher than that of carbon steel. During the dry-wet cycle, the wetting time will affect the type of corrosion products. When the wetting time is short, the corrosion products are mainly β-FeOOH. With the prolonging of the wetting time, the corrosion products gradually transform to γ-FeOOH.