Enhanced corrosion inhibition of S235JR steel using anionic clay–phenolic extract hybrids: findings of synergistic action

Corrosion of mild steel in marine environments poses a major challenge for industrial sustainability. This study aims to develop an eco-friendly corrosion protection approach by combining phenolic extracts (PE) from extremophile plants with Zn₂-Al-layered double hydroxides (LDH) to form hybrid inhibitors for S235JR steel in artificial seawater (3.5% NaCl). Three plant extracts were evaluated for their antioxidant potential, and <i>Cynomorium coccineum</i> was identified as the most active candidate. The hybrid material was synthesized via anion-exchange, and structural integrity was confirmed by XRD, FTIR, and SEM analyses, showing that the incorporation of organic compounds did not alter the crystallinity of the LDH matrix. Electrochemical measurements using the Tafel polarization revealed that the hybrid system achieved a corrosion inhibition efficiency of 60%, surpassing LDH alone (38%) and the phenolic extract alone (45%). This improvement confirms a synergistic effect resulting from the combined adsorption and controlled release mechanisms. These findings demonstrate the potential of combining bioactive plant molecules with inorganic carriers as a sustainable and low-cost strategy for corrosion control in marine applications.