Eashwar M, Lakshman Kumar A, Sreedhar G, Kennedy J, Suresh Bapu R H
a CSIR - Central Electrochemical Research Institute , Corrosion Research Centre , Mandapam Camp - 623519 , Tamil Nadu , India.
Biofouling. 2014 Sep;30(8):929-39. doi: 10.1080/08927014.2014.952632.
The influence of sunlight of varying intensity on the performance of UNS S30400 stainless steel (SS) was explored under conditions of natural biofilm development in coastal seawater. In a series of tests performed outdoors under an opaque roof, a range of shades were fashioned to impart varied amounts of diurnal light. These were an ambient level where the underwater illumination was ~ 5% of full sunlight, two intermediate ranges of lighting with ~ 2.5% and ~ 1% of the daylight, and a condition of full darkness. In comparison with the dark, increments of sunlight rendered the SS progressively less aggressive as cathodes in galvanic couples with UNS C70600 alloy. Likewise, welded SS with pre-initiated localized corrosion sites exhibited substantially lower rates of propagation with light. Thus, biofilms and sunlight affected cathodic kinetics in opposite ways. Surface analytical tests showed that the accumulation of manganese (Mn) within the biofilms was small relative to reports from waters of lower salinity. These results not only reveal that extremely low amounts of sunlight are adequate to offset the microbial effect, but also highlight the lack of convincing evidence for Mn cycling as a potent mechanism for enhanced cathodic kinetics in full-strength seawater.
在沿海海水中自然生物膜形成的条件下，研究了不同强度阳光对UNS S30400不锈钢（SS）性能的影响。在一系列在不透明屋顶下进行的户外试验中，制作了一系列遮阳装置，以提供不同量的日间光照。这些光照条件包括：水下光照约为全日照5%的环境水平、两种光照强度分别约为日光2.5%和1%的中间范围，以及完全黑暗的条件。与黑暗环境相比，阳光照射量的增加使SS在与UNS C70600合金形成的电偶中作为阴极的腐蚀性逐渐降低。同样，带有预先引发的局部腐蚀点的焊接SS在光照下的腐蚀扩展速率也显著降低。因此，生物膜和阳光对阴极动力学的影响方式相反。表面分析测试表明，与低盐度水域的报告相比，生物膜中锰（Mn）的积累量较少。这些结果不仅表明极少量的阳光就足以抵消微生物的影响，还突出了缺乏令人信服的证据证明锰循环是海水中增强阴极动力学的有效机制。
