Over a six month period, UT measurements at a matrix of measurement sites on a Fractionation column indicated
that it was suffering from severe internal corrosion. It was decided to monitor hydrogen flux at all measurement
points on a frequent basis. The resulting flux profiles broadly co-trended. Time averaged flux and longer term
corrosion rates correlated well. In a more sophisticated treatment, flux data was converted into hydrogen activity at
the corroding face, to compensate for hydrogen permeation through the steel, thus normalising any variations in
steel temperature and thickness. Again the correlation of activity and shorter term corrosion rate was good, with a
correlation factor that was closely comparable to that obtained from laboratory data. In short, the data illustrates
that, at temperatures where naphthenic acid corrosion can take place, hydrogen flux may provide a keen indication
of the corrosion rate in near real time, with the diffusive delay in flux stabilization upon a corrosive change
typically being one hour.
Keywords: naphthenic acid corrosion, hydrogen flux, visbreaker