Development of conductive fractal copper–polypyrrole nanocomposites for dual corrosion inhibition and ammonia detection in metallic food containers

Abstract

In the present study, we present the development and characterization of a polypyrrole (PPy)-based nanocomposite embedded with fractal copper (Cu) crystals, engineered to provide enhanced corrosion resistance and ammonia-sensing capability for metallic food packaging. The nanocomposite coatings were prepared by electrodeposition on industrial tinplate electrodes in oxalic acid (PPy@OxAc) and sodium salicylate (PPy@NaSa) media. Structural analyses via SEM and AFM revealed distinct morphologies with copper crystallization forming leaf-like fractal structures, promoting high surface roughness and contact angles (96° for PPy@OxAc and 93° for PPy@NaSa), indicating hydrophobicity advantageous for corrosion resistance. Corrosion performance, evaluated through open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization in a 3 % NaCl solution, demonstrated an over 95 % inhibition efficiency. This was evidenced by a significant decrease in corrosion current density from 2.238 μA/cm² to 0.083 μA/cm² over immersion times up to 144 h. Ammonia exposure tests highlighted a significant and reversible increase in resistance upon NH₃ exposure, linked to electron or proton transfer mechanisms in the PPy matrix. These results support the dual function of Cu–PPy nanocomposites in providing prolonged corrosion protection and real-time detection of spoilage indicators, marking a substantial step toward sustainable and intelligent food packaging solutions.