Black powder formation is an oxidative corrosion process that over time can cause operational
problems as the solids collect within the system. There is a net weight gain within the system
as molecular oxygen becomes incorporated as part of the solid materials. A novel quartz
crystal microbalance (QCM) test apparatus has been developed to determine the effectiveness
of various corrosion inhibitors to prevent black powder formation in sales gas pipelines. The
QCM measures minute changes in frequency of a quartz crystal with weight gain/loss. For our
test apparatus, the QCM crystal was coated with iron where small increases in mass due to
oxidation of the iron layer are recorded as a drop in frequency. Using the Sauerbrey equation,
the drop in frequency observed during corrosion testing can be converted to a corrosion rate.
Several inhibitor chemistries were tested using the QCM apparatus. In this study it was found
that a new oil-soluble corrosion inhibitor is the most effective for preventing black powder
formation under the sales gas conditions.
Keywords: Black powder, corrosion testing, carbon dioxide corrosion, oxygen corrosion,
corrosion inhibition, QCM