Corrosion inhibition of carbon steel under two‐phase flow (water‐petroleum) simulated by turbulently agitated system

Abstract

The corrosion of carbon steel in single-phase (water with 0.1N NaCl) and two immiscible phases (kerosene-water) using turbulently agitated system was investigated. The experiments were carried out for Reynolds number (Re) range of 38 000 to 95 000 using circular disc turbine agitator at 40 • C. In two-phase system, test runs were carried out in aqueous phase (water) concentrations of 1% vol, 5% vol, 8% vol, and 16.4% vol mixed with kerosene at various Re. The effect of Re, percent of dispersed phase, dispersed droplet diameter, and number of droplets per unit volume on the corrosion rate were investigated and discussed. Test runs were carried out using two types of inhibitors: sodium nitrite of concentrations 20, 40, and 60 ppm and sodium hexapolyphosphate of concentrations 485, 970, and 1940 ppm in a solution containing 8% vol aqueous phase (water) mixed with kerosene (continuous phase) at 40 • C for the whole range of Re. It was found that increasing Re increased the corrosion rate and the presence of water enhanced the corrosion rate by increasing the solution electrical conductivity. For two-phase solution containing 8% vol and 16% vol of water, the corrosion rate was higher than single phase (100% vol water). The main parameters that play the major role in determining the corrosion rate in two phases were concentration of oxygen, solution electrical conductivity, and the interfacial area between the two phases (dispersed and continuous). Sodium nitrite and sodium hexapolyphosphate were found to be efficient inhibitors in two-phase solution for the investigated range of Re.On aétudié la corrosion de l'acier au carbone dans des conditions monophasiques (eau avec 0,1N de NaCl) et diphasiques immiscibles (kérosène-eau)à l'aide d'un système agité turbulent. Les expériences ontété menées pour une gamme de nombre de Reynolds (Re) de 38000à 95000, avec un agitateur de type Rushtonà 40 • C. Des tests pour le système diphasique ontété effectuées dans des concentrations de phase aqueuse (eau) de 1%, 5%, 8% et 16,4% en volume, mélangéeà du kérosène pour différentes valeurs de Re. L'effet du nombre de Reynolds (Re), le pourcentage de la phase dispersée, le diamètre des gouttelettes dispersées et le nombre de gouttelettes par unité de volume sur le taux de corrosion aété etudié et analysé. Les essais ontété réalisés avec deux types d'inhibiteurs: du nitrite de sodiumà des concentrations de 20, 40 et 60 ppm et de l'hexapolyphosphate de sodiumà des concentrations de 485, 970 et 1940 ppm dans une solution contenant 8% en volume de phase aqueuse (eau) mélangéeà du kérosène (phase aqueuse)à 40 • C pour la gamme complète de Re. On a trouvé que l'augmentation du Re augmentait le taux de corrosion et que la présence d'eau améliorait le taux de corrosion en augmentant la conductivitéélectrique des solutions. Pour la solution diphasique contenant 8% et 16% en volume d'eau, le taux de corrosion est plus grand qu'en monophasique (100% en volume d'eau). Les principaux paramètres qui jouent un rôle majeur dans la détermination du taux ...

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