Multidimensional\nHybrid Metal Phosphonate Coordination\nNetworks as Synergistic Anticorrosion Coatings

In the technologically important field of anticorrosion\ncoatings,\nit is imperative to form well-defined and characterized films to protect\nthe metal surface from corrosion. Phosphonate-based corrosion mitigation\napproaches are currently being exploited. Herein, the synergistic\naction of alkaline-earth metal ions and two carboxy-diphosphonates,\nPAIBA [<i>N,N</i>-bis(phosphonomethyl)-2-aminoisobutyric\nacid] and BPMGLY [<i>N,N</i>-<i>bis</i>(phosphonomethyl)glycine],\nis explored. Also, a family of four novel hybrid metal phosphonate\nmaterials is reported, Mg-PAIBA, Ca-PAIBA, Sr-PAIBA, and Sr-Na-PAIBA,\nwhose topological analysis revealed a variety of underlying networks\nwith the 6,10T9, <b>unc</b>, SP 1-periodic net (4,4)(0,2), and\nunique topologies. The synergistic metal/carboxy-diphosphonate blends\nwere tested for their anticorrosion performance on carbon steel at\npreselected concentrations (0.1–1.0 mM) and pH values (4.0–6.0).\nThe results showed an enhanced inhibitory performance in the presence\nof metal cations at higher concentrations. The inhibition of corrosion\nat pH 5.0 in the presence of BPMGLY, PAIBA, and their combination\nwith Sr<sup>2+</sup> was investigated in detail using electrochemical\nmeasurements. Enhanced inhibition was achieved with a 1:1 Sr<sup>2+</sup>/BPMGLY (or PAIBA) binary system. Polarization curves indicated that\nthe system is a “mixed” inhibitor. This study widens\nthe family of carboxyphosphonate coordination polymers, showing their\npotential as attractive hybrid coatings with anticorrosion performance.