AH32耐蚀钢显微组织对其腐蚀行为的影响

根据《油船货油舱耐蚀钢性能标准》规范,通过浸泡实验测量了AH32耐蚀钢在货油舱底部模拟环境中的腐蚀过程.采用失重测量、电化学极化与阻抗方法、扫描电镜和电子探针等手段,分析了AH32耐蚀钢显微组织对其腐蚀行为的影响.实验结果表明:模拟货油舱底板腐蚀实验中,AH32耐蚀钢的轧制面因珠光体所占面积分数小而腐蚀速率较低,其横截面则因珠光体面积分数大而造成腐蚀速度较快,而且二者的腐蚀速度均随浸泡时间的延长而加速.此外,轧制面表面有均匀腐蚀和因夹杂物溶解所形成的蚀坑,而横截面的腐蚀则沿条带状珠光体组织而有选择的进行.样品的珠光体区域在浸泡后有碳富集,这是造成腐蚀随浸泡时间延长而加速的原因.

INFLUENCE OF MICROSTRUCTURE OF AH32 CORROSION RESISTANT STEEL ON CORROSION BEHAVIOR

International martime organization(IMO) has approved< Performance standard for corrosion resistant steel for cargo oil tanks of oil tankers>and considered corrosion resistant steel as the only alternative for anti-corrosion coating since May 2010.The implementation of the standard will have a profound impact on ship building,steel,shipping and other industries.At present,Japan has a relatively mature technology,South Korea has completed the pre-development work,while China has only carried out some preliminary studies.If the technology is blocked,a large number of steel needs to be imported which would push up the cost of construction of the shipbuilding industry,and has a direct impact on the orders of shipping enterprises.The amount of steel for cargo oil tank in China is more than two million tons each year,and therefore,the localization of research and application of corrosion resistant steel for cargo oil tanks has become an urgent task.The impact of microstructure of the existing shipbuilding steel on corrosion behavior in simulated corrosion environment is studied based on the standard in this paper to develop our own corrosion resistant steel.According to the standard,immersion test was used to measure the corrosion process of AH32 corrosion resistant steel in the bottom simulated environment of cargo oil tanks.Using gravimetric measurement, electrochemical polarization and impedance methods,scanning electron microscopy and electron probe et al,the influence of microstructure of AH32 corrosion resistant steel on its corrosion behaviors was analysed.The experimental results showed that:during the test simulating the corrosion of the bottom plate of cargo oil tanks,corrosion rate of the rolling surface of AH32 corrosion resistant steel was low with small area fraction of pearlite,corrosion rate of the cross section was fast due to the big area fraction of pearlite,and both corrosion rate increased with the immersion time.In addition,there were uniform corrosion and the pits formed by dissolved inclusions in rolling surface,and corrosion of the cross-section was selected along the banded pearlite.The carbon enriched in pearlite area of the sample after immersion,which caused corrosion rate increased with the immersion time.