经16年实海暴露腐蚀试验，在国内首次发现921等含铬低合 金钢在榆林和青岛站海水中出现了耐蚀性“逆转”现象.用金相法、SEM/EDS法、细菌鉴定法 、化学分析方法，以榆林站的921钢海水锈层为重点研究对象，对试验钢的锈层进行了综合 性分析研究了“逆转”的原因.初步查明，某些含铬钢耐蚀性“逆转”的主要原因是，经较 长时间的海水腐蚀，由于麻点腐蚀的深入发展，产生了比碳钢、无铬钢严重得多的金属小颗 粒的“脱落”，对腐蚀速率作了较大贡献.并认为，在实海腐蚀1年左右，碳钢和低合金钢的 腐蚀动力，可能由氧扩散控制逐渐变为硫酸盐还原菌(SRB)等细菌腐蚀控制.
Through exposure corrosion test in seawater for 16 years,the “reversion” phenomena of corrosion resistance of containing chromium low alloy steels such as 921 in Yulin and Qingdao seawater were first found in China,but the reason was not understood at home and abroad.In order to study the reason of “reversion”,several methods including metallography,SEM/EDS,bacteri a identification and chemical analysis were used for entirely investigating the r ust layer on test steels and the rust layer on 921 steel exposed in Yulin seawat er was emphasized on.The reason of corrosion resistance “reversion” of some co ntaining chromium low alloy steels in seawater has been initially found out.As t he seawater corroded for a long period,the corrosion pits deeply developed and m any small metal granules fell off substrate,that greatly contributed to corrosio n rate.“Falling off” containing chromium steels was much serious than carbon s teels and non-containing chromium steel.It is considered that the corrosion dyna mic of carbon steels and low alloy steels may change from oxygen diffusion contr ol to bacteria such as SRB corrosion control at about one year.
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