Corrosion Study of Carbon Steel Used by Sonatrach International Society, Protected by a Primer by Electrochemical Impedance Spectroscopy in a Deaerated Simulated Soil

摘要

The Electrochemical Impedance Spectroscopy (EIS) and the variation of corrosion potential wereused to examine on a carbon steel of type X60A nuance, used on pipelines manufacturing, in adeaerated solution of a simulated soil of pH= 8.1.The reference was an uncoated carbon steel sample and the thickness of the deposited primer was25 μrn. The nature of coating and its thickness were chosen as close to real "systems" employed onpipelines.The evolution of performance and the degradation of steel uncoated and painted have been studiedin a range of frequencies between 10~5 and 5.10~(-4) Hz for a period of 63 days. The results obtained from Nyquist diagrams show the existence of several electrochemical phenomena characterised by different time constants. In the case of uncoated steel, only one loop was observed corresponding to the degradation of the metal. With samples of coated steel, two capacitive loops exist: the first characterises the behaviour of the organic coating, the second the behaviour of the substrate.