X70管线钢渗铝层盐雾腐蚀后能谱面扫描分析

EDS analysis of aluminized coatings on X70 pipeline steel after salt spray corrosion

利用激光热效应对X70管线钢进行渗铝处理,研究了其在5%盐雾试验中的腐蚀行为,通过SEM、EDS和XRD等手段对腐蚀产物表面-界面形貌、化学元素面扫描和物相组成进行了分析,探讨了渗铝层耐盐雾腐蚀机理。结果表明,渗铝层界面由渗铝层、扩散层和基体组成,Al和Fe原子在扩散层相互扩散,形成了FeAl2金属化合物相,是界面冶金结合的主要机制;盐雾腐蚀以点蚀为主,表面出现裂纹是热扩散过程中热应力作用的结果;腐蚀后渗铝层界面中存在Al和O元素的分层富集现象,形成的Al2O3氧化膜有效地阻止Cl-对基体金属的腐蚀,Al在渗铝层的局部富集是保护基体的主要因素,提高了X70管线钢的耐盐雾腐蚀性能。

Aluminizing treatment was eonducted on surface of a X70 pipeline steel with laser thermal effect, and corrosion behavior of the aluminized coatings in 5% salt spray test was investigated. The surface-interface morphology, microstructure and phase component of the coatings were analyzed by means of SEM, EDS and XRD. The mechanism of salt spray corrosion of the aluminized coatings was discussed. The results show that the aluminized coatings are composed of aluminized layer, diffusion layer and substrate. The elements of A1 and Fe are diffused each other in the diffusion layer, forming a intermetallic eompound phase of FeA12, that is the main mechanism of the metallurgical binding of the interface. The pitting corrosion in the aluminized coatings is the main mode for salt spray corrosion. The surface cracking is a result of thermal stress. There is a stratified enrichment of AI and O elements in the aluminized coating interface, forming a layer of AI2 03 film to effectively prevent C1- from eroding the substrate metals, and the A1 enrichment is a main factor of protecting the substrate, improving the properties of salt spray corrosion for XT0 pipeline steel.