极地低温海洋大气环境下Ni-Cr-Mo-V钢腐蚀行为与室内外相关性研究

Correlation of Corrosion Information Aquired by Indoor Acceleration Testing and by Real Low Temperature Marine Atmosphere Exposure in Polar Region for Ni-Cr-Mo-V Steel

通过腐蚀失重、扫描电镜、激光共聚焦显微镜等测试方法对Ni-Cr-Mo-V钢在室内加速试验和中山站户外暴露试验后的腐蚀行为进行了对比研究。结果表明:Ni-Cr-Mo-V低合金高强钢在极地低温大气环境下腐蚀速率为11.3μm/a,腐蚀产物由Fe_(3)O_(4)、γ-FeOOH、α-FeOOH和β-FeOOH组成,腐蚀产物中大量的β-FeOOH表明低温环境下生成的锈层保护性较差。低温大气腐蚀以均匀腐蚀为主,冻融循环引起试样表面的电解质浓度变化,导致了锈层下点蚀的形成。在冻融循环过程中,锈层中水分由于固液相变引起的应力变化以及锈层与金属基体热胀系数的不同导致了锈层开裂。

In order to investigate the applicability of the proposed indoor accelerated test spectrum,which aims to simulate the low temperature marine environment in the polar region,and the corrosion mechanism of low alloy steel exposed in the real polar low temperature atmospheric environment,therefore,the Ni-Cr-Mo-V steels were subjected to indoor accelerated test in lab and to outdoor exposure test in Zhongshan station at the polar region respectively,then the corrosion behavior of the tested steels was comparatively studied by means of mass loss measurement,scanning electron microscope,and laser confocal microscope.The results revealed that the corrosion rate of the steel is 11.3μm/a,and the corrosion products are composed of Fe_(3)O_(4),γ-FeOOH,α-FeOOH and β-FeOOH.The presence of the large amount of β-FeOOH indicates that the rust scale formed in low temperature environment has poor protectiveness.The low temperature atmospheric corrosion is mainly uniform corrosion.The freeze-thaw cycle causes the alteration of electrolyte concentration on the surface of test steel,which results in the formation of pitting corrosion beneath the rust scale.During the freeze-thaw cycle,the alternation of stresses caused by the cyclical solid-liquid phase transition of the water in the rust scale and the difference of the thermal expansion coefficient between the rust scale and the metal matrix could lead to the cracking of the rust scale.