Low water volumes associated with gas production can lead to salt deposition under conditions that allow water evaporation to occur within a pipeline system. Salt deposits are capable of attracting water vapor from wet gas that has a water content well below the normal dew point. This phenomenon is related to the hygroscopic or deliquescent properties associated with individual salts present in the deposits. The relative humidity at which liquid water starts to accumulate at salt deposits is referred to as the Deliquescence Relative Humidity (DRH). Both MgCl_2 and CaCl_2 have strong abilities to attract water and are typical components in gas line salt deposits. This means those components will attract water from the gas, even if the water content is well below the theoretical dew point, and form concentrated salt solutions. These concentrated brines lead to aggressive, localized pitting corrosion. In order to better understand the contribution of deliquescence to the corrosion mechanism in gas pipelines where salt deposits can form, a novel laboratory test method was developed to simulate the deliquescence phenomenon in gas pipelines. This paper gives a brief explanation of DRH, reports findings of this laboratory study and concludes that deliquescence is an integral part of the corrosion mechanism.
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