Effect of Oil/Water Intermittent Wetting on CO₂ Corrosion in the Presence of Acridine and Myristic Acid

The effect of a paraffinic model oil (LVT-200)-containing select surface-active compounds (myristic acid and acridine) on CO₂ corrosion with and without intermittent wetting has been studied. Observations have shown that the presence of myristic acid in the oil phase does not affect the corrosion behavior due to its lack of partitioning in the water phase. However, after direct contact between the oil phase-containing myristic acid and the metal surface, there was a significant decrease in the corrosion rate. This phenomenon gradually diminished at pH 4.0 but was more persistent at pH 6.5. The presence of acridine in the oil phase was shown to have a strong inhibitive effect at pH 4.0, even during the partitioning step. The partitioning of acridine from the oil phase to the water phase at pH 4.0 was confirmed by ultraviolet-visible spectroscopy results. However, there was no inhibitive effect conferred by the presence of acridine on the corrosion rate at pH 6.5. An experimental methodology was developed that facilitated improved simulation of the effect of intermittent oil/water wetting on CO₂ corrosion. The electrochemical current response during the oil/water intermittent wetting cycles showed that the persistency of model oil (without surface-active compounds) on the mild steel surface is only a matter of seconds. Corrosion rate measurements showed that the presence of myristic acid renders the oil layer more persistent after intermittent wetting compared to one-time direct contact.