On the Mechanism of Atmospheric Rusting of Iron and Protective Rust Layer on Low Alloy Steels
On the Mechanism of Atmospheric Rusting of Iron and Protective Rust Layer on Low Alloy Steels
复制标题
铁的大气生锈机理及低合金钢的保护锈层
DOI：
10.3323/jcorr1974.23.1_17
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发表时间：
1974
期刊：
影响因子：
--
通讯作者：
S. Shimodaira
中科院分区：
文献类型：
--
作者：
T. Misawa;K. Hashimoto;S. Shimodaira
研究了常温下铁和钢的重要大气腐蚀产物Fe3O4、α-FeOOH、γ-FeOOH、δ-FeOOH和无定形氢氧化铁在水溶液中的形成机理。最终产物的形成过程受氧化速率、pH值以及铁的初始和中间种类的结构和组成的强烈影响。给出了铁的中间体、氧化物和氢氧化物的形成过程示意图，其中包括铁的溶解态和固态态。低碳钢和低合金钢在大气暴露试验中的锈蚀过程，可以根据所示图用r-FeOOH、无定形氧氧化铁和a-FeOOH的形成机理来解释。在铁锈中发现了大量的无定形物质，通过红外和远红外光谱鉴定为无定形氧化铁，FeOx(OH)3-2x。在低合金钢表面形成的非晶态氢氧化铁锈具有大量结合水的特点。结果表明，r-FeOOH溶解后再沉淀得到的非晶态氢氧化铁能够均匀覆盖在低合金钢上，这是因为低合金钢中所含的Cu和P有利于钢的均匀溶解，有利于r-FeOOH在钢表面的均匀形成。含有结合水的无定形氧化铁形成致密、无裂纹的锈层，作为防止大气腐蚀的保护屏障。干湿循环和含SO2的气氛有利于低合金钢表面形成稳定的保护锈层，这是由于在生锈过程中铁和r-FeOOH的溶解加速以及无定形氢氧化铁的析出。
The mechanism of formation of green rusts, Fe3O4, α-FeOOH, γ-FeOOH, δ-FeOOH and amorphous ferric oxyhydroxide, which are important atmospheric corrosion products of iron and steels, in aqueous solution at room temperature, has been investigated. The formation processes on which end products are determined are strongly affected by the oxidation rate, pH and the structure and composition of initial and intermediate species of iron. The schematic diagram of formation processes of intermediates, oxide and oxyhydroxides of iron has been presented, in which both dissolved and solid species of iron are included. The rusting process of mild and low alloy steels during atmospheric exposure test can be interpreted by the mechanism of formation of r-FeOOH, amorphous ferric oxyhydroxide and a-FeOOH on the basis of presented diagram. A large amount of amorphous matter found in rust was identified by infrared and far infrared spectra as amorphous ferric oxyhydroxide, FeOx(OH)3-2x. The amorphous ferric oxyhydroxide rust formed on low alloy steel was characterized by considerable amount of bound water. It was concluded that the amorphous ferric oxyhydroxide obtained by reprecipitation after dissolution of r-FeOOH is able to cover uniformly on low alloy steel, because Cu and P contained in low alloy steel contribute to uniform dissolution of steel and facilitate uniform formation of r-FeOOH on steel surface. The amorphous ferric oxyhydroxide containing bound water forms a dense, crack-free rust layer, which acts as protective barrier against atmospheric corrosion. The wet-dry cycle and the atmosphere containing SO2 favor the formation of stable protective rust layer on low alloy steel due to the acceleration of dissolution of iron and r-FeOOH and precipitation of amorphous ferric oxyhydroxide in rusting process.