动静态服役环境下SPHC钢腐蚀行为对比

Comparison of Corrosion Behavior of SPHC Steel under Dynamic and Static Service

目的研究SPHC钢在不同服役环境下腐蚀行为的差异性。方法采用户外暴露法对SPHC钢进行长达18个月的动静态暴露试验,取样时间分别为暴露后的3、6、9、12、18个月。通过腐蚀动力学测试、SEM(扫描电子显微镜)、XRD(X射线衍射)、电化学测试,分别评价SPHC钢在一定时长大气暴露后的平均腐蚀速率、腐蚀产物形貌、腐蚀产物成分以及锈层的耐蚀性。结果暴露3个月时,动态暴露下SPHC钢的腐蚀速率和锈层厚度均大于静态暴露试样,在暴露6个月时被静态暴露试样反超。随后,动静态暴露下SPHC钢的腐蚀速率均缓慢下降,锈层厚度逐渐增加。动态试样表面检测出静态试样表面未检测到的β-FeOOH和SiO_(2),动态试样自腐蚀电流小于同期的静态试样,锈层电阻则相反。结论由于动态暴露过程中服役环境不断变化,导致SPHC钢初期腐蚀产物中含有β-FeOOH和SiO_(2),增大初期试样表面的反应活性区域,加速初期腐蚀。随着暴露时间的延长,β-FeOOH和SiO_(2)虽然使得SPHC钢难以形成如静态暴露般均匀致密的锈层,但是提高了锈层电阻,增强了SPHC钢的耐蚀性,抑制了腐蚀反应的发生。

This paper aims to compare the difference of the corrosion behavior of SPHC steel under different service conditions.The outdoor exposure method is used to conduct dynamic and static exposure tests on SPHC steel for up to 18 months,and conduct sampling after 3,6,9,12,18 months respectively of exposure.Through corrosion kinetics test,SEM(scanning electron microscope),XRD(X-ray diffraction),electrochemical test,respectively,the average corrosion rate,corrosion product morphology,corrosion product composition and corrosion resistance of SPHC steel are evaluated after a certain period of atmospheric exposure.The results show that,after 3-month exposure,the corrosion rate and the thickness of the rust layer of SPHC steel after dynamic exposure are larger than those after static exposure,but are overtaken by those after 6-month static exposure.Subsequently,the corrosion rate of SPHC steel after both dynamic and static exposures slowly decrease,while the thickness of the rust layer gradually increase.Theβ-FeOOH and SiO_(2),which are rare on the surface of SPHC after static exposure,are detected on the surface of SPHC after dynamic exposure.The self-corrosion current of dynamic sampling is smaller than that of the static sampling at the same period,but the rust resistance is opposite.Due to the continuous changes in the service environment during the dynamic exposure process,the initial corrosion products of SPHC steel containβ-FeOOH and SiO_(2) impurities,which increase the reactive area on the initial sample surface and accelerate the initial corrosion.As the exposure time increases,although these impurities make it difficult for SPHC to form a uniform and dense rust layer like static exposure,the resistance of the rust layer improves,enhancing the corrosion resistance of SPHC,and inhibiting the occurrence of corrosion reactions.