Study Of The Electrochemical Characteristics Of Micro-organisms Attached To The Marine Environment And The Detection And Control Methods

The most effective method to solve microbiological influenced corrosion and biofouling is to prevent and control the adhesion and growth of the biofilm. First of all, it's necessary to find the responds of biofilm development by electrochemical method or biological method. The electrochemical parameters influenced by marine biofilm were studied by electrochemical method and epifluoresence microscopy for six kinds of coastal-used metals. Among them, the relationship between the electrochemical parameters of passive metal and microbes adhesion was elaborated. At last, the influence of environment factors on the activity of biofilm was studied and the validity of several biofilm prevention methods was evaluated by this relationship. Main results are summarized as follows:1) The electrochemical parameters of six kinds of metals were studied in natural seawater. And results showed that, for passive metals, the effect of biofilm on their electrochemical characteristics was remarkable, especially the ennoblement of open circuit potential. Therefore, these metals can be chose to study the state of biofilm on metal surface.2) There was a linear relationship between the potential ennoblement of passive metals with the adhesion microbes number on metal surface in natural seawater. And it was proved that this ennoblement was caused by the decrease of passivation current of metals as a result of biofilm formation. 3) Considering the potential of brass is almost a constant for long time in seawater, brass electrode can be seen as a reference to measure the open circuit potential of passive metal(such as high Mo steel). This high Mo steel-brass compound electrode can be used to inspect and evaluate the adhering ability of microbes in seawater. 4) Using the relativity between potential ennoblement and bacteria activity, we found that the higher temperature of seawater increased the activity of bacteria. Change of pH had little influence on the formation of biofilm. High salinity or desalt of seawater can all reduced bacteria activity. Adding nutrition cannot advance the growth speed and activity of bacteria in natural seawater.5) Bactericide can kill almost all the plankton in natural seawater, but useless to the remove of biofilm already formed on metal surface. Scraping can remove biofilm quickly but need frequently, because after one day there was new biofilm formed, alike the effect of ultrasonic disposal.6) Cathodic polarization treatment can kill microbes near the metal surface, which prevent the further adhesion of bacteria to metal surface. But cathodic polarization has no effect on the exterior microbes of biofilm. 7) The open circuit potential change of passive metals can be used to monitor the influence of environment factors on microbes, and evaluate the validity of several control methods.