IMPROVING THE INHIBITIVE PERFORMANCE OF DIBENZYL SULFOXIDE FOR PICKLING OF STEEL IN SULFURIC-ACID

Possibilities for the use of dibenzyl sulfoxide (DBSO) in pickling of mild steel in sulfuric acid (H2SO4) solutions were explored. The addit ion of DBSO in the pickling solution had no adverse effect on the pick ling rate, but its efficiency in inhibiting corrosion of the base meta l was unsatisfactory. To improve this, thiourea (TU), copper cations ( Cu2+), and chloride ions (Cl-) were incorporated with DBSO and were fo und to provide a synergistic effect. An optimized composition (OC) of 0.01% DBSO + 0.02% copper sulfate (CuSO4 . 5H(2)O) + 0.2% sodium chlor ide (NaCl) provided optimum performance. Addition of higher concentrat ions of Cu2+ in the bath accelerated the corrosion rate. The influence s of temperature, acid strength, and exposure time on the OC performan ce of the inhibitor also were studied. The steady-state corrosion pote ntial in the presence of the OC was not affected considerably compared to that in the blank solution. The cathodic and anodic curves in the presence of inhibitors were shifted in the lower current density regio n with no change in the Tafel slopes. The mechanism of the inhibitor a ction also was discussed.