On line monitoring systems of MIICON Cu-10Ni alloy in brackish water

The alloy ASTM B-III UNS C70600 (Cu-1ONi) has been extensively used for surface condenser tubes in power stations. However, there have been cases of Microbiologically Induced Corrosion (MIC) in this alloy caused by Sulfate-Reducing Bacteria (SRB). This paper presents the evaluation of Alloy C70600 in a dynamic monitoring system with one-way circulation using brackish water (Lake Maracaibo water) with and without chlorine treatment, for 3,6,8 and 12 months exposure period. The physical-chemical results indicated favorable conditions for microbial development with planktonic SRB present in the order of 107 cell/ml SEM, EDXA, WDX and XRD analysis evidenced organic and inorganic fouling, Cu2S (Chalcocite) and Cu2O (Cuprite) as the corrosion product and the characteristic MIC onset morphology. The electrochemical tests indicated that the corrosion current increased with the chlorine content (4.0 A/cm2/0.0 ppm Cl2, 6.0 u A/cm2/0.1 ppm Cl2 and 16.0 A/cm2/2.0 ppm Cl2). Furthermore, the polarization curves did not show passivation of this alloy. All these results suggest that Alloy C70600 is not resistant to MIC in brackish water even with chlorine treatment. (Author)