Protection of carbon steel corrosion in 3.5% NaCl medium by aryldiazonium grafted graphene coatings

Abstract

Corrosion protection efficiency of graphene was enhanced by modifying the surface of graphene-coated carbon steel (CS/G) using aromatic molecules. Aniline, 1-naphthylamine, and 1,8-diaminonaphthalene were utilized to synthesize three diazonium salts: phenyl diazonium (PD), 1-naphthyldiazonium (1ND), and 1,8-naphthyldiazonium (1,8ND). The prepared salts were grafted to graphene via formation of covalent C–C bonds. This modification led to restoring graphene surface defects and consequently increasing its corrosion protection efficiency. Molecular bindings were characterized using XRD, SEM-EDXA, FT-IR, and Raman techniques. The results confirmed bonding of phenyl groups to the graphene surface. Then, anti-corrosion performance of modified graphene-coated carbon steel in 3.5% NaCl was evaluated by weight loss, electrochemical methods such as potentiodynamic polarization (Tafel), and electrochemical impedance spectroscopy (EIS). The data showed that restored graphene coatings offer a better corrosion resistance than the non-restored graphene. The number of phenyl rings and azo groups affected charge transfer resistance (R_ct), corrosion potential (E_corr), current density (I_corr), and the slope of the anodic and cathodic reactions (β_a,c), demonstrating that the proposed modification method will hinder corrosion reactions. Moreover, the increase in protection efficiency was in order of CS/G-1,8ND > CS/G-1ND > CS/G-PD. The CS/G-1,8ND showed maximum protection efficiency of 98.8% in comparison to the others. Finally, anti-corrosion ability of the proposed modified graphene surface route was further confirmed by contact angles measurements and surface methods i.e., SEM and EDXA. Observed results are presented and discussed.