Dewpoint corrosion is a well-known phenomenon in refinery overheads, where fine water droplets condense from the vapor upon cooling, and the acid gases in the vapors diffuse into water droplets to form a highly corrosive low pH liquid. We have identified a similar mechanism in hydrocarbon liquids (HLs), which we call as Nucleation Corrosion.

HLs leaving warm separators are saturated with dissolved water (DW), which even in the presence of corrosive species such as organic acids (OAs) are not corrosive. Upon cooling, the DW nucleates as sub-micron free water droplets and organic acids present in the HL partition into the water droplets decreasing pH to ~3. These highly acidic water droplets cause aggressive corrosion, called ‘Nucleation Corrosion’ (akin to dew point corrosion), where acids diffuse from liquid hydrocarbon to water nuclei. We present a systematic method to study, elicit the effect of OAs and H2S, temperature gradients and hydrocarbon composition as well as ways to mitigate Nucleation Corrosion.

Further, our initial data suggests that nucleation corrosion may occur in refinery overhead naphtha reflux lines that have both high levels of OAs and insufficient insulation.