San-Der Chyou

Investigations of the biological corrosion of condenser tubes by scanning auger microprobe techniques

Abstract A duration test was conducted at the inlet bay of Hsin-Da Power Plant in Taiwan to study the roles of macro-organisms and micro-organisms in facilitating or inhibiting the microbiologically influenced corrosion (MIC) of metal alloys in seawater. A significant amount of fouling organisms was grown on the attachment plate submerged in the field for 56 and 92 days. Copper toxicity resulted in little fouling but slight corrosion still occurred on the copper plate. Titanium was found to be 100% fouled by the fouling organisms. Stainless steel plate was found to have the worst MIC corrosion among the tested samples. After mechanically peeling off the polychaeta and barnacle organisms, samples were analyzed by the scanning Auger microprobe (SAM). SAM results indicate that sodium, oxygen and sulfur accumulated on the MIC regions of the sample surfaces covered by the fouling organisms, and chlorine and nitrogen were distributed in the regions compensating for the local distributions of sodium, oxygen and sulfur. It was proposed that the development of a thick macro-fouling mass will cause the anaerobic zones to develop on the metal surface, wherein the MIC processes are accelerated.