The influence of the addition of sodium dodecyl sulfonate to sodium caprylate on the corrosion inhibition of carbon steel in aqueous HCl

Sodium caprylate (SC) and a SC + sodium dodecyl sulfonate (SC + SDS) mixture were studied as corrosion inhibitors for carbon steel (CS) in aqueous HCl at different inhibitor concentrations, temperatures, HCl concentrations, and immersion times. The maximum corrosion inhibition efficiency of 87.9% for SC was achieved within 1 h of CS immersion in 40 mM SC, while adding only 5 mM to SC boosted the inhibition efficiency to 94.2%. After 48 h of immersion, the corrosion inhibition efficiency was maintained, slightly increasing to ca. 89% for SC and ca. 98% for SC + SDS. The high inhibition performance was maintained even at higher temperatures. The Tafel polarization curves suggested that both SC and SC-SDS act as mixed-type inhibitors. The inhibition mechanism was suggested to occur through forming a barrier/hydrophobic-type SC and SC + SDS layer irreversibly adsorbed on the CS surface. SC and SDS were found to interact with the CS surface through their carboxylate and sulfonate groups, respectively.[GRAPHICS].