Microfouling on cathodically protected mild steel in sea water

The influence of cathodic protection on the rate of microfooling on mild steel was investigated in natural seawater. Cathodic protection was applied at current densities of 0.12 and 0.22 mA/cm2 using sacrificial zinc anodes. The rate of attachment of bacteria and diatoms was observed to increase dramatically as a function of applied current, particularly during the first few days of exposure. It was also found that sulphate-reducing bacteria come into the scene as early as the fourth day white freely corroding specimens encourage SRB activity only by the twelfth day of exposure. The growth rate of calcareous depos~tsw as also investigated to make it comparable with that of microorganisms

Marine microbial films and the corrosion of steel

Succession of aerobic and anaerobic bacterial films on mild steel has been studied for 100 days in two contrasting seawater sites at Mandapam. The relation between primary film microfouling and initiation of anaerobic corrosion has been attempted The ecological aspects in anaerobic corrosion beneath marine fouling are discussed in the light of the results of present work and already available data on marine corrosio

A possible role for phototrophic sulphur bacteria in the promotion of anaerobic metal corrosion

Bacteria associated with the biological sulphur cycle play a particularly dominant role in the process of metallic corrosion. This is largely due to the ubiquitous presence of these bacteria in natural environments1,2. Unsurprisingly, sulphatereducing bacteria have been the main highlight in numerous bio-corrosion investigations. A vast number of mechanisms3–8 have been proposed in the literature to explain the rather multifarious process of anaerobic corrosion. The deterioration of iron and concrete by aerobic sulphur bacteria (thiobacilli) is more straightforward. These bacteria oxidize sulphur and/or sulphide to sulphuric acid9

Biofouling studies relating to cathodic protection of some metals in seawater

Biofouling studies relating to the cathodic protection of mildsteel, stainless steel and brass in seawater have been conducted in the shallow waters of mandapam coast, to understand the role of biological factors operating. Rationale for the investigations were the response to cathodic protection of marine fouling, the occurence and growth rate of calcareous deposits. Cathodic protection to the metals was effected using zinc. Results indicate that the severity of fouling on mildsteel and brass is increased and inhibition of fouling on stainless steel is obtained due to cathodic protection. Barnacles, the chief calcareous shell dwelling group were found to occur with selective abundance on cathodically protected mildsteel and brass panels, with a significant increase in their shell size. These organisms were found to contribute largely to the calcareous deposits on mild steel and brass and to a smaller extent on stainless steel. The selective abundance of barnacles on cathodically protected mildsteel and brass is discussed in the light of the chemical, biological and electrochemical bases for their gregariousnes

Occurrence of thiobacilli in Tuticorin harbour waters

107-109The number of thiobacilli obtained as colony forming units on thiosulphate agar was the highest ever reported from marine sources. Seven isolates, out of 15 from enrichment cultures, were Thiobacillus spp., T. thiooxidans and T. ferroxidans produced the most acidic conditions in liquid cultures. Laboratory experiments with decaying alga Ulva lactuca in seawater showed that thiobacilli were involved in the oxidation of protein sulphur. The study not only indicates the status of pollution in harbour waters but also shows that thiobacilli may have wide distribution in coastal waters

Marine fouling and corrosion studies in the coastal waters of Mandapam, India

Results of a comprehensive study on marine fouling conducted in the coastal waters of Mandapam, India, are presented. Based on data from different tests, the effects of fouling organisms on the phenomena of corrosion and cathodic protection are discusse

Progressions of phototrophic bacteria and sulphur chemistry in decomposition models

Decomposing cultures of macro-organisms in sea water, with no added mineral media, produced faithful enrichments of phototrophic sulphur bacteria. The enrichments brought about spectacular colouration of the sea water solutions and specific bacterial progression, depending on the type of decomposing biomass. These patterns were remarkably consistent in enrichments from geographically isolated marine locations on the east coast of India. Chemical analysis of sea water in decomposition experiments with or without lighting indicated incomplete sulphide oxidation by the phototrophs, yielding primarily elemental sulphur. Contrary to the presumption that marine sponges are the only exceptional aerobic habitat for phototrophic sulphur bacteria, the present results strongly suggest that these anaerobic bacteria may generally subsist in association with macro-organisms and are prevalent in coastal waters

Sunlight-enhanced calcareous deposition on cathodic stainless steel in natural seawater

In replicate series of experiments in natural seawater, one in full darkness and the other in a 1:1 diurnal cycle with as little as 5% of natural solar illumination, sunlight promoted calcareous deposition on cathodic stainless steel surfaces. As exemplified by scanning electron microscopy, the deposit that formed under the natural diurnal cycle, in the presence of photosynthetic biofilms, was composed of finer calcareous crystals that provided more compact and more uniform surface coverage than the one formed in the dark. The light-enhanced deposit also possessed better scale properties, as suggested by X-ray analysis and electrochemical measurements. Sunlight enhancement of calcareous deposition looked all the more conspicuous when day and night regimes were examined independently. These results not only bear important implications for cathodic protection in marine waters, but also provide an intriguing analogy to coral reef calcificatio

Epidemiology of alcohol consumption in an urban area of Kancheepuram district, Tamil Nadu

Introduction: In India, the ever increasing production, promotion, distribution, and the easy availability and accessibility of alcohol together with the changing values in the society have resulted in alcohol consumption becoming one of the major public health problems. Aims: The study was undertaken to find out the prevalence of alcohol consumption and its epidemiological determinants in an urban area of Kancheepuram district, Tamil Nadu. Methodology: This descriptive cross-sectional study was done among adult males above 18 years of age in Anakaputhur area of Kancheepuram district, Tamil Nadu. Simple random sampling method was used to select the study participants to reach the required sample size of 400. Pretested structured questionnaire was used as study tool to collect data regarding alcohol consumption practices. Data were analyzed using SPSS version 22. Results: The prevalence of alcohol consumption among the study participants was found to be 39%. The major determinants of alcohol consumption which were found to be statistically significant were age less than 45 years, those belonging to a nuclear family, those who consume tobacco, consumption of alcohol by family members, those who did not receive advice regarding harmful effects of alcohol from family members, those having stigma of being a nondrinker among friends/peers and those having awareness of health problems caused due to alcohol consumption. Conclusion: This study shows that it is high time we change the approach of educating the public about the effects of alcohol consumption by intensive behavioral change continuum activities at a younger age group, coupled with encouraging refusal skills to overcome peer pressure