Investigation of microgalvanic activity of carbon steel API 5L X52 in presence of Amine corrosion inhibitors by scanning vibrating electrode technique (SVET).

Microgalvanic activity of carbon steel API 5L X52 was investigated by scanning vibrating electrode technique (SVET). Two types of corrosion inhibitors were used for the protection of carbon steel. The first one is based on primary amine function with linear carbon chain (inhibitor A). The second one contains primary amine with Ethylene oxide branched chain (inhibitor B). The evolution of microgalvanic activity was studied at different imposed currents ranging up to 200 mA without and in the presence of 20 ppm and 50 ppm of each corrosion inhibitor. In absence of inhibitors, the maps given by SVET analysis showed a uniform microgalvanic activity with imposed currents ranging from 0 to 1 mA and tend towards less cathodic area. For high imposed currents (10mA, 25mA, 50mA, 100mA and 200mA); a clear evolution in the microgalvanic activity is noticed considering the presence of several anodic area. The dissolution of the carbon steel was accelerated and the microgalvanic potential tends to electronegative values. With the corrosion inhibitors, no anodic area was observed for weak currents ranging from 0 to 10mA. The best protection is assured by the inhibitor B due to the improvement of its solubility. Beyond 25 mA, the protection from corrosion decreases but inhibitor B still demonstrates a better efficiency. [ABSTRACT FROM AUTHOR]