Organic corrosion inhibitors protect the metal by forming a hydrophobic film on the metal surface, which provides a barrier to the dissolution of the metal in the electrolyte. To sustain the protective film, a certain minimum inhibitor concentration should be maintained in the solution, usually designated as corrosion inhibitor residual. If the residual falls below the minimum concentration, then the adsorbed layer will start to degrade leaving the carbon steel surface unprotected. Globally, water-soluble corrosion inhibitor residuals are measured from water sample. For low water-cut oil systems, collecting a water sample is difficult, especially considering the safety concerns related to Bottom of Line (BOL) traps. A review held during 2017 within Petroleum Development Oman (PDO) Company, led to the suspension of BOL activities because of HSE risk, which impacted the residual monitoring in low water-cut system.

This paper explains the developed method which is a modified version of the industrial standard methyl-orange colorimetric titration method1 . It is based on the extraction of a water-soluble corrosion inhibitor from an oil sample by further methyl-orange titration of cation-active component. The test method has been successfully applied with a minimum root mean square error (R2 ) value of 0.93.

Subject
Test methods, Water, Inhibitor performance, Extraction, Absorbance, Titration, Calibration, Pipelines, Petroleum, Corrosion inhibitors, Corrosion monitoring, Samples, Oil
Keywords:
Corrosion monitoring, Corrosion control, Chemical treatment, Water-soluble Corrosion inhibitors, Corrosion Inhibitor Residual, Low water-cut system, colorimetric, spectrophotometric titration method
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2021
Association for Materials Protection and Performance (AMPP)
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