Predictive Model for CO2 Corrosion Engineering in Wet Natural Gas Pipelines

Starting from a “worst case” corrosion rate prediction with the deWaard-Milliams equation, correction factors can be applied to quantify the influence of environmental parameters and corrosion product scale formed under various conditions. Equations are proposed for each factor. A low-temperature scale formed in condensing water can cause a reduction in the top-of-the-live corrosion rate in pipelines. At higher temperatures, a more protective scale forms even under high liquid flow rates. The decrease of corrosion rates caused by dissolved Fe is accounted for with a pH correction factor. The effect of the presence of a liquid hydrocarbon phase is included. Equations are presented that enable the effect of glycol injection on corrosion to be calculated along the length of a pipeline. Combinations of effects in the model are discussed.