Inhibition of Steel Corrosion in HCl by Derivatives of Cinnamaldehyde: Part I. Corrosion Inhibition Model

A general chemisorption model is proposed that yields a rate expression consistent with the quantitative structure-activity relationship (OSAR) developed by Hansch. Even complex inhibition mechanisms may be amenable to this treatment. For example, t-cinnamaldehyde (TCA) and many of its derivatives undergo slow polymerization subsequent to adsorption, leading to formation of a thickening film that gives the steel added protection. This reduction in corrosion rate correlates with molecular structure in a qualitatively similar manner to the rate decrease induced by adsorption. Thus, the Hansch OSAR is applicable. It is also argued that surfactants, which greatly increase the efficacy of TCA and its derivatives, do not change the relative effectiveness of the inhibitors, and the Hansch OSAR is again suitable for modeling the trends in corrosion rates.