Fabrication and characterization of novel p-Phenylamine-N(4-chloro salicylaldenemine) ligand and its metal complexes and evaluation their anti-corrosion and chemical resistance properties in epoxy/SiO2 nanocomposite for steel surface coating

Abstract

Schiff base metal complex/epoxy nanocomposite coating engineering is considered a vital corrosion protection model for steel surface applications. To support this concept, several metal (Cr(III), Co(II), Ni(II), Cu(II) and Zr(IV)) complexes of Schiff base ligand named p-Phenylamine-N(4-chloro salicylaldenemine) (HL) were synthesized. The HL was chelated with metal ions as a bidentate manner through NO donor atoms with 1:2 (metal:HL) molar ratio and it was detected by microanalytical procedure. The resulting metal chelates of HL were fully characterized using the conductivity and magnetic moment measurements, UV–Vis, FT-IR, 1H NMR, XRD and TG-DTG analysis. Transmission electron microscope (TEM) and X-ray diffraction (XRD) techniques were accomplished for the silica nanoparticles characterization. Different surface-modified epoxy/SiO2 nanocomposite coating formulations with HL and its metal complexes were prepared without any compatibility problems. The anti-corrosion behavior of the epoxy nanocomposite coated films versus unmodified conventional epoxy was clarified by salt spray accelerated corrosion test. The obtained results demonstrated a considerable improvement in the rust grade, size and frequency of blistering, and adhesion strength of surface modified Ni(II) and Cr(III) complexes nanocomposite coated steel films at the same loading level. To confirm the previous concept, SEM morphology survey and FT-IR chemical structure characterizations for the employed cured coated films after the direct exposure to salt spray aggressive fog were investigated. Chemical immersion strategy was performed to check the acids and alkali resistances of nanocomposite coated films against conventional epoxy. The perfect protective behavior of the Ni(II) and Cr(III) complexes may be attributed to their highly effective magnetic moment (μeff) which leads to enhancing the cross-linking density through the coating layer, thereby enhancing the adhesion between the steel substrate and epoxy matrix.