Study Pitting Corrosion of P110 Steel by Electrochemical Frequency Modulation Technique and Coupled Multielectrode Array Sensor

By using the electrochemical frequency modulation (EFM) technique, coupled multielectrode array sensor (CMAS), and other corrosion research techniques, the pitting corrosion behavior of P110 steel in oilfield formation water was studied. The results showed that serious pitting corrosion was observed on P110 steel at 90°C in oilfield formation water. The EFM and CMAS techniques could be used for monitoring or detecting pitting corrosion effectively. The average corrosion rates obtained by EFM and CMAS both decreased with time. At the first 12 h of the test the average corrosion rate was quite high and general corrosion occurred, and then the average corrosion rate decreased and the pitting corrosion was observed from the EFM results. The CMAS result showed that when the pitting corrosion happened, there were obvious localized anode and cathode pots on the metal surface that directly caused the pitting corrosion and might be related to the structure of the protective layer.