碳含量和浸泡时间对碳钢热带自然海水腐蚀产物中细菌组成的影响

COMPOSITION OF BACTERIA IN CORROSION PRODUCT OF CARBON STEEL WITH DIFFERENT CARBON CONTENT IMMERSED IN SEAWATER FOR DIFFERENT TIME

为了深入探讨海洋微生物对碳钢的腐蚀机理,通过细菌的分离鉴定方法,研究了不同碳含量碳钢在自然海水中浸泡不同时问后腐蚀产物中的细菌组成。结果表明不同碳钢每克表面刮取物中需氧菌及兼性厌氧菌的数量均在浸泡时间为91d时达最大值,而硫酸盐还原菌的数量在浸泡时间为184d时达最大值。铁细菌和硫细菌的变化不明显。不同碳钢,除7d实验周期外,随碳含量增加,腐蚀产物中需氧菌及兼性厌氧菌有增加趋势,而硫酸盐还原菌却存在降低趋势。需氧菌及兼性厌氧菌主要由两个菌属的细菌组成,即假单胞菌属和弧菌属,当浸泡时间达1a时,还出现大量黄杆菌。从各个菌属所占比例可见,碳钢腐蚀产物中菌群初期主要由需氧菌组成,随着浸泡时间延长,兼性厌氧菌开始占据主要地位。铁细菌主要是由瑙曼氏菌属和鞘铁菌属组成。不同细菌在生长过程中对氧的需求与消耗及代谢产物的差异,会对碳钢的腐蚀过程产生不同的影响。

Bacterial adhesion and biofilm formation on the surface of carbon steel are common in seawater. The heterogeneous biofilm and the associated bacteria form complex biological systems that impact the physical and chemical characters of the metal/biofilm interface, such as pH, dissolved oxygen, chloride and sulfate, etc., and change the corrosion mechanism of carbon steel. Accordingly, it is important to investigate the bacteria composition in the corrosion product of carbon steel. In this work, the bacteria compositions in the corrosion product of different carbon steel emerged in seawater for different periods were researched by bacteria isolating and identifying methods. The results show that the contents of aerobe and facultative anaerobe reach the maximum value when the corrosion time is 91 d. However, the content of sulfate reducing bacteria reaches the maximum value when the corrosion time is 184 d. The contents of iron bacteria and sulfur bacteria change irregularly. For different carbon steel, except 7 d corrosion time, the contents of aerobe and facultative anaer- obe in biofilm increase with increasing the content of carbon, but that of sulfate reducing bacteria descends. Aerobe and facultative anaerobe mainly compose pseudomonas and vibrio. When the corrosion time is 365 d, fiavobacterium also exists in the corrosion product. The aerobe is predominant in the initial stage of experi- ment and facultative anaerobe is predominant in later stage. The major composition of iron bacteria includes naumanniella and siderocapsa. The different bacteria produce the different metabolic products that influence corrosion process of carbon steel.