Influence of functionalized polyhexamethyleneguanidines on the electrochemical characteristics of metals in a methanesulfonate electrolyte

In aqueous methanesulfonate electrolytes, the adsorption behavior of modified cationic polyelectrolytes on zinc and iron electrodes was investigated. A pronounced dependence of the adsorption free energy on the degree of incorporation of carboxyl and aromatic functional groups into the polymer chains was established. The individual contributions to the free energy of oligomer adsorption on metal surfaces were quantified. Increasing the degree of functionalization strengthens the interaction between the organic adsorbate and the metal interface. It simultaneously suppresses solvent-induced desorption of macromolecules, attributable to the enhanced hydrophilicity of the polymer chains. The adsorption equilibrium constants of the oligomers were significantly higher on zinc compared to Armco iron, a difference attributed to variations in surface charge and hydrophilicity at the applied potentials. The highest corrosion inhibition efficiency in mildly acidic media was observed for polyelectrolytes modified with aromatic groups, predominantly due to a steric inhibition mechanism.