Study of the Corrosion Inhibitive Effect and Adsorption Process of Two Azo-Aldehydes on Carbon Steel in 1 M H₂SO₄

Two aromatic aldehydes with azo linkage (AS1 and AS2) were assessed for their inhibitive effect on carbon steel corrosion in 1 M H₂SO₄. The inhibition efficiency was studied by gravimetric and electrochemical analysis. The effects of concentration and temperature on the inhibition efficiency have also been studied. The obtained results showed that both of the used compounds can be considered as efficient carbon steel corrosion inhibitors. The compound which has methyl group in its structure (AS2) has higher inhibition efficiency (93.11% with 0.2 mM at 303 K by electrochemical analysis) than the one with cyano group (AS1). The adsorption isotherms of the inhibitors were studied; it was found that the adsorption of the two compounds obeys Langmuir isotherm. The studied inhibitors are mixed type inhibitors and adsorbed onto the surface of the carbon steel by a physisorption process. SEM and AFM techniques were used to study the effect of the aggressive solution on the morphology of the metal surface in the absence and presence of the used inhibitors.