Investigation of Pitting Corrosion of Carbon Steel in Rich Diglycolamine Units

Pitting corrosion of carbon steel in rich diglycolamine solutions from gas sweetening units was investigated using potentiodynamic cyclic anodic polarization. potentiostatic measurements, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) techniques. The solution used contained 28000 ppm hydrogen sulfide cyclic polarization curves, which is evidence on the occurrence of pitting corrosion. SEM observations confirmed the existence of pits on the electrode surface, Plant data from absorption tower and heat exchanger pipes con:finned these results, Increasing the size of hysteresis loop with temperature indicates that tendency to pitting corrosion increases in rich amine solution. Because of the dependence of the values of Epa and ~ to scan rate in cyclic curves, the exact values for pitting potential and protection potential were obtained from potentiostatic curves. By increasing the temperature, E¢t and ~ decreased. EDS micro analysis showed that there was no :film or very poor :film with low sulfur contents in pits, in compare with the unaffected surface ofpits.

Keywords:

carbon steel A516 Or 60 , pitting corrosion , Diglyoolamine (DGA) , cyclic polarization , potetiostatic