带氧化皮Q345q钢在模拟西北典型大气环境中的腐蚀行为研究

2021-05-06 16:42:18 作者：张延文来源：材料研究学报分享至：

摘要

采用XRD、扫描电子显微镜、电化学技术、干湿交替腐蚀试验研究了Q345q钢的热轧氧化皮结构及其在三种模拟西北几种典型大气环境中的腐蚀行为，并探讨了不同介质环境下热轧氧化皮的破坏机理和锈层形成机理。结果发现，热轧氧化皮的相组成主要是Fe3O4和Fe2O3，氧化皮的结构为多孔状，并带有裂纹等缺陷；带氧化皮钢在进行干湿交替加速腐蚀实验后，虽然在NaHSO3溶液中腐蚀增重最高，但自腐蚀电位随腐蚀时间的延长增大，腐蚀后期自腐蚀电流密度减小，锈层保护性较好；而在除冰盐介质中的腐蚀速率最小，主要发生以Cl-为主的点蚀，形成“大阴极-小阳极”腐蚀特征，而且含有β-FeOOH、HFeCl4（H2O）6等腐蚀产物，导致锈层疏松脱落，锈层的自腐蚀电流密度增大，锈层不具保护性；在除冰盐+NaHSO3溶液中，既发生点蚀又伴随全面腐蚀，由于Cl-和HSO3-的协同作用，降低了一部分Cl-的自催化效应，但多数α-FeOOH是由β-FeOOH转化而来的，锈层保护性不强。

关键词：金属材料 ; Q345q钢 ; 氧化皮 ; 除冰盐 ; NaHSO3 ; 混合溶液 ; 西北典型大气

Abstract

The structure of the oxide scale on the as received hot-rolled bridge steel Q345q and the corrosion behavior of the steel Q345q with oxide scale in three simulated atmospheric environments in Northwest China were studied by XRD, scanning electron microscopy, electrochemical technique and wet-dry alternating corrosion test. The results show that the hot-rolled oxide scale composes mainly of Fe3O4 and Fe2O3, which is porous with cracks and other defects. After the dry-wet alternating accelerated corrosion test of the steel Q345q with oxide scale, although the corrosion weight loss is the highest in NaHSO3 solution, the free-corrosion potential increases with the corrosion time, and the free-corrosion current density decreases in the later stage of corrosion. As far as the morphology of the rust layer and the ratio of γ/α* are concerned, the rust layer formed on the steel presents good stability; However, in deicing salt solution, the corrosion rate is the smallest, but the steel suffered mainly from Cl--dominated pitting corrosion with the corrosion characteristics of “large cathode and small anode”. Its corrosion products contain such as β-FeOOH and HFeCl4（H2O）6, which results in loose rust layer with poor protectiveness and increased free-corrosive current density; In deicing salt+NaHSO3 solution, both pitting corrosion and general corrosion occur. Due to the synergistic effect of Cl- and HSO3-, the autocatalytic effect of a part of Cl- is reduced, but most α-FeOOH is converted from β-FeOOH, which resulted in the poor protective rust layer.

Keywords： metallic materials ; Q345q steel ; oxide scale ; deicing salt ; sodium bisulfite ; mixed solution ; typical atmosphere in northwest China