两种新型Ni-Cr-Mo-V钢在模拟海水环境中的腐蚀行为对比研究

Comparative Study on Corrosion Behavior of Two Novel Ni-Cr-Mo-V Steels in Simulated Seawater Environment

采用浸泡实验、电化学实验和微观形貌观察研究了两种Ni-Cr-Mo-V钢(A钢和B钢)在海水环境下的腐蚀行为与机制。结果表明,两种钢腐蚀阳极和阴极电化学过程一致,但B钢表现出较正的腐蚀电位和较低的腐蚀电流密度。A钢中夹杂物类型为CaS-MgO-Al_(2)O_(3),尺寸在3~5μm之间,活性夹杂物引发局部腐蚀;B钢主要为Al_(2)O_(3)夹杂物,其尺寸在1~3μm之间,且诱发局部腐蚀的程度较轻。长周期腐蚀42 d后,两种钢均发生均匀腐蚀。两种钢腐蚀产物层分为致密的内锈层和疏松的外锈层,A钢锈层厚度大于B钢,且A钢中内锈层中纵向分布的裂纹降低了锈层的保护性。

The corrosion behavior of two novel Ni-Cr-Mo-V steels(steel A and steel B)in a simulated seawater environment was comparatively investigated by means of immersion test,electrochemical test,and microscopic observation.The results indicate that the cathodic and anodic electrochemical processes in the corrosion process of the two steels are consistent,while the steel B shows a more positive corrosion potential and lower corrosion current density.The main inclusions in steel A is CaS-MgO-Al_(2)O_(3)with sizes ranging from 3 to 5μm,which act as active sites of localized corrosion initiation;in comparison,the Al_(2)O_(3)inclusions in steel B with sizes ranging from 1μm to 3μm,the tendency of localized corrosion induced by which is relatively light.After long-term corrosion for 42 d,the two steels all show uniform corrosion with bilayered corrosion product scale composed of a dense inner rust layer and a loose outer rust layer.However,the thickness of the rust scale of steel A was greater than that of steel B.Besides,there existed longitudinal cracks in the inner rust layer of steel A,which may deteriorate the protective property of the rust scale.