Sour Corrosion Rate Correlation
Sour corrosion rates can be confidently predicted from flux only if the corrosion is contingent upon removal of corrosive scale to reveal bare steel. The correlation indicated in the chart is based on laboratory experiments1 and field experience with scale free steel in the range of 5-50 oC, 40-120 oF. More confident correlation can be expected by direct comparison of averaged flux with wall loss data over the same period, in specific scenarios. It should be noted that sour corrosion is far more episodic than commonly realized; wall loss measurements providing an average corrosion rate over a long time span. In the chart below, the upper boundary for the corrosion rate estimate is less well defined than the lower boundary.
1 F.W.H.Dean, C.M.Fowler, R.Farnell, S.J.Mishael, ‘Hydrogen flux and corrosion rate measurements on hydrogen induced cracking susceptible and resistant A516 steels in various sour environments’, Corrosion 2010, Paper 10179, Conf. series, NACE, Houston, 2010