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Mitigating T Carbon Dioxide Corrosion in Wet Gas Systems op-of-the-line (TOL) corrosion in wet gas pipelines occurs when water condenses in the presence of corrosive gases such as carbon dioxide (CO 2) and hydrogen sulfide (H2S).1 When water condenses in the presence of acid gases, the freshly condensed water is acidic and corrosive. TOL corrosion occurs where heat transfer rates are high in the presence of a temperature gradient near the pipe wall. One commonly used technique to mitigate TOL corrosion is a batch chemical treatment application that involves the delivery of a liquid slug of corrosion inhibitor (CI) between two batching pigs to cover the entire surface of the inner pipe, and maintain a protective inhibitor flm.2 A variety of continuously injected chemical methods have been proposed to prevent TOL corrosion. Volatile CIs (VCIs) typically act as pH stabilizers, providing control of pH and reducing Sunder ramachandran, Vladimir JoVanciceVic, and TOL corrosion rather than active corroPatrick rodgerS, Baker Hughes, Inc., Sugar Land, Texas sion inhibition. This article reports the ibraheem a. ahmed, Texas A&M;, College Station, Texas results of a laboratory study of the inhibimaSlat al-Waranbi, Saudi Aramco, Dhahran, Saudi Arabia tion of TOL corrosion by various volatile amine inhibitors using a new technique, the quartz crystal microbalance (QCM), under simulated TOL conditions. The QCM enables the measurements of condensation and corrosion rates. Top-of-the-line (TOL) corrosion in wet gas subsea production or gathering lines is often prevented by using corrosion-resistant alloys or batch corrosion inhibition Experimental Procedures programs. Both options are expensive or marginally Quartz Crystal Microbalance Methodology efective. Using a quartz crystal microbalance-based Minute changes in the frequency of a quartz crystal are measured in a QCM, and these are associated with a weight gain/loss proportional to the frequency change.3 The Sauerbrey equation relates change in mass with change in frequency.3 Increases in the frequency of the crystal allow us to calculate the change of mass of the deposited flm. Figure 1 shows the custom-built UNS N10276 test vessel used in this work. A laboratory methodology, a new efective TOL corrosion inhibitor was developed. Te product provides corrosion inhibition in wet gas systems, has a good environmental profle, and excellent compatibility with various materials. 56 MATERIALS PERFORMANCE May 2013 NACE International, Vol. 52, No. 5