Study of the corrosion products formed on carbon steel surface in hydrochloric acid solution

Effect of an antibacterial drug, sulfacetamide, IUPAC name N-[(4-aminophenyl) sulfonyl] acetamide (APSA), on the corrosion products formed on carbon steel surface in 1.0?mol?L^?1 HCl solution has been investigated using mass loss, X-ray photoelectron spectroscopy (XPS), and simultaneous thermal and differential scanning calorimetry/differential thermal analysis (TG/DSC/DTA). Mass loss measurements reveal that the corrosion rate of carbon steel is retarded by APSA and that the inhibition efficiency of this inhibitor increases with increasing the concentration. XPS analysis shows that, at this stage, the main product of corrosion is a non-stoichiometric Fe³⁺ oxyhydroxide, consisting of a mixture of FeO(OH) in anhydrous or hydrated forms, containing Cl^? inclusions and adsorbed APSA molecules. The mechanism of inhibition was discussed in light of the chemical structure of the investigated inhibitor. The corrosion products were analyzed using TG/DSC/DTA technique.