Eco-Friendly Hybrid Materials for Steel Protection Using a Water-Soluble Polyamic Acid as Chelating Agent

High Resolution Image Download MS PowerPoint Slide In this study, an environmentally friendly waterborne coating was developed as a corrosion inhibitor for mild steel (MS) through the synthesis of a polymeric dispersion. Initially, a water-soluble polyamic acid (PAmA) solution was synthesized utilizing ethylenediaminetetraacetic dianhydride and 2,2-(ethylenedioxy)bis(ethylamine). The incorporation of ether linkages and amic acid functional groups into the polymer backbone generates numerous polar sites, thereby facilitating the formation of a stable aqueous organosilane dispersion predominantly composed of 3-glycidoxypropyl trimethoxysilane (GPTMS), without the use of surfactants or additional salts. Additionally, 25 wt % of GPTMS can be replaced with tetraethyl orthosilicate (TEOS), which serves primarily as a crosslinking agent and a precursor for nanosilica, resulting in an aqueous organic/inorganic dispersion under optimized conditions. Comparative analyses with reference samples, such as polyacrylic acid dispersion, demonstrated a higher degree of condensation of 94.6% for the organic/inorganic dispersion in PAmA, as confirmed by Raman spectroscopy and 29 Si-NMR following sol-gel reactions. These results indicate the formation of extensive cross-linking sites and a silica network, which serves as passive layers, yielding a thermal decomposition temperature exceeding 380 °C for the organic/inorganic layer produced by the PAmA polymer. Notably, the application of the PAmA solution not only enhanced cross-linking density and facilitated the formation of a silica network for the organic/inorganic dispersion but also provided the formation of imide structures, leading to a robust sol-gel-derived hybrid coating system, consistent with findings from FTIR and DSC analyses. Consequently, this study demonstrates the successful development of an eco-friendly corrosion inhibitor that exhibits outstanding performance in salt spray tests and superior corrosion protection efficiency (η = 99.7%), as determined by electrochemical impedance spectroscopy for MS.