ELECTROCHEMICAL NOISE IN ASSESSING MIC IN OFFSHORE INJECTION SYSTEMS

摘要

The results of a preliminary study of electrochemical noise measurements (ENM) on the API 5L X52 pipeline steel in presence of aerobic bacteria are presented. The 16S rRNA gene sequence was used in order to identify the bacteria strain with a high precision. The sequence analysis suggests that it may be a new bacterial specie. The long-term noise time records show that during the bacterial logarithmic growth stage, the pipeline steel generates irregular oscillations, typical of localized corrosion, while in the constant growth stage, the irregular oscillations diminish. Moreover, the long-term time records show that the noise patterns generated in a solution without bacteria were typical of a coupled mechanism of localized and uniform corrosion. We found evidence that support the electrochemical noise measurements. Also, apparently the oscillations in current noise reach a regular pattern during the logarithmic growth phase. The statistical analysis of raw data shows that the mean noise potential changes from positive to negative values in presence of the bacteria. Compared to test without bacteria, the noise resistance diminishes in presence of the bacteria during the logarithmic growth stage. Finally, the localized parameter raises near to 1 during the same stage where the metal undergoes localized corrosion.