School of Chemistry, Federal University of Rio de Janeiro, Brazil.
National Institute of Technology, Rio de Janeiro, Brazil.
Colloids Surf B Biointerfaces. 2018 Dec 1;172:43-50. doi: 10.1016/j.colsurfb.2018.08.026. Epub 2018 Aug 16.
This work aimed to identify microbial colonization and biocorrosion in welded seam areas of API 5 L X65 carbon steel, since microorganisms are ubiquitous and there is a lack of information on their biological and electrochemical interactions with these structures. In the present study, polished and unpolished welded coupons prepared by shielded metal arc welding were assayed to identify the effect of surface roughness and local changes in the metal microstructure on microbial colonization. Experiments were performed in glass cell vessels with fresh and sterile seawater to establish the presence or absence of microorganisms. For comparison, nonwelded coupons were simultaneously tested as a control. On the 15th day, both polished and unpolished welded coupons and the nonwelded coupons immersed in fresh seawater showed microbial colonization, though the corrosion products were more abundant for the welded coupons. Nevertheless, unpolished welded coupons showed a higher predominance of pitting around the beads than polished coupons. These results suggest that filler material creates conditions more favorable for biofilm development, thus intensifying the localized corrosion on the welds. It can be concluded that adhesion and subsequent biocorrosion are directly influenced by surface roughness, whereas microstructural modifications due to welding interfere little with microbial adhesion, regardless of the greater pit depths compared to those of nonwelded coupons. Additionally, although open circuit potential measurements indicated that metal surfaces are protected when coated with biofilms, pitting corrosion was more pronounced in welded coupons immersed in fresh seawater than in those immersed in seawater without microorganisms. Therefore, the use of open circuit analysis alone is not recommended for biocorrosion monitoring of welded coupons.
本工作旨在研究 API 5L X65 碳钢焊接缝区域的微生物附着和生物腐蚀情况，因为微生物无处不在，而关于它们与这些结构的生物电化学相互作用的信息却很缺乏。在本研究中，对经过抛光和未抛光的屏蔽金属电弧焊接制备的焊接试片进行了检测，以确定表面粗糙度和金属微观结构的局部变化对微生物附着的影响。实验在装有新鲜和无菌海水的玻璃电池容器中进行，以确定是否存在微生物。为了进行比较，同时对未焊接的试片进行了测试作为对照。在第 15 天，浸入新鲜海水中的抛光和未抛光焊接试片和未焊接试片都出现了微生物附着，尽管焊接试片的腐蚀产物更为丰富。然而，未抛光的焊接试片在焊缝周围的点蚀比抛光试片更为突出。这些结果表明，填充材料为生物膜的发展创造了更有利的条件，从而加剧了焊缝的局部腐蚀。可以得出结论，粘附和随后的生物腐蚀直接受到表面粗糙度的影响，而焊接引起的微观结构变化对微生物的粘附影响很小，尽管与未焊接试片相比，焊接试片的点蚀深度更大。此外，尽管开路电位测量表明，当金属表面被生物膜覆盖时会受到保护，但在新鲜海水中浸泡的焊接试片中，点蚀腐蚀比在没有微生物的海水中浸泡的焊接试片中更为明显。因此，不建议单独使用开路分析来监测焊接试片的生物腐蚀。
