Electrochemical Behavior of drogen Sulfide

Electrochemical behavior of A516 Gr60 carbon steel in Diethano1amine (DEA) solutions containing hydrogen sul:fide (lI.2S) at pH=1O.2 was investigated. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were performed at various temperatures within the range of 25°e to 800e and different concentrations of DEA. Results obtained showed that in the presence of H2S, a meta-stable passive sulfide :film is funned on the su.rfilce and corrosion current density is increased. By increasing temperature and amine concentration, corrosion potential and icon- increased and passive stability region decreased. Nyquist plots from EIS results revealed two time constants fur corrosion processes; a capacitive loop with a depressed semicircle at high frequencies due to charge transfer and a straight line at low frequencies region due to Warburg diffusion. The EIS results were then fitted with equivalent circuits. Results obtained indicated that diffusion of Fe2+ ions (produced from anodic dissolution) and atomic hydrogen (Hj (produced from reduction of HS· ions) across the sulfide :film is a rate determining step. Warburg coefficient (s) extracted from Randles plots (Zre Vs 0)11l) decreased by increasing the amine concentration and this indicates that compaction of sul:fide film has decreased. By increasing the temperature, the diameter of the first capacitive loop decreased.

Keywords:

carbon steel A516 , Diethanolamine (DEA) , electrochemical impedance spectroscopy , poetntiodynamic polarization