The stability constant of the protective film of corrosion inhibitors

• F.B. Shevlyakov^1,2 and O.R. Latypov¹

¹ Ufa State Petroleum Technological University, Kosmonavtov str., 1, 450064 Ufa, Russian Federation
² LLC “RN-BashNIPIneft”, Lenin str., 86/1, 450006 Ufa, Russian Federation

Abstract: Liquids of oilfield media are extremely variable, they usually consist of several phases and are subject to changes in composition under the influence of pressure and temperature. The complexity of protecting pipelines from corrosion is due to the multiphase and layered flow of the pumped medium. The accepted calculation of the specific consumption of the corrosion inhibitor for the consumption of the treated liquid using the technology of constant or periodic dosing can lead to excessive or insufficient inhibition of pipelines. The formation and maintenance of the protective “film” is carried out due to the diffusion of the active substance of the inhibitor from the liquid volume to the metal surface of the pipeline wall. The speed of formation of a protective film on the metal surface of pipelines depends on the dosage of the inhibitor. Its stability on the surface of the protected metal depends primarily on the properties of the inhibitor and on the hydrodynamic parameters of pumping. The article proposes the calculation of the specific flow rate of the corrosion inhibitor taking into account the geometric parameters of the pipeline and the hydrodynamic characteristics of the gas-liquid flow. For this purpose, the corrosion inhibitor index is introduced – the stability constant of the protective film, which characterizes the ability of the corrosion inhibitor to be adsorbed and retained on the surface of the pipeline. The effective dosage of the corrosion inhibitor, determined on a field pipeline or well for the possibility of replication to similar objects, requires recalculation based on the characteristics of the pipeline and the flow structure, depending on the content of the gas phase. Recalculation of the effective dosage of the corrosion inhibitor revealed that the essential parameters are the ratio of the fractions of the liquid and gas phases and the radius of the pipeline. The free gas phase of the pumped medium, depending on the laminar and turbulent flow regime, also determines the flow structure. Recalculation of the effective dosage through the stability constant will allow both to prevent overspending of the reagent or to increase it to meet the requirements imposed by mining companies for the effectiveness of corrosion inhibitors.

Keywords: corrosion inhibitor, stability constant, pipeline, flow structure, minimum effective dosage

Int. J. Corros. Scale Inhib., 2023, 12, no. 3, 825-841
doi: 10.17675/2305-6894-2023-12-3-2

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