Corrosion protection ability of hydrophobic zinc based coordination polymers on mild steel surface

A series of Zn2+ based hydrophobic coordination polymers (CPs) have been synthesized by varying methylene spacers length (m = 1 to m = 6) of aliphatic dicarboxylic acids followed by reaction with the zinc acetate by using hydrothermal method. The synthesized CPs were coated on the mild steel (MS) specimens to investigate the effect of methylene spacers length of dicarboxylic acids on hydrophobicity and corrosion behavior. The synthesized CPs and their coatings on MS have been characterized by various instrumental techniques such as Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), Field Emission Scanning Electron Microscopy (FE-SEM), water contact angle (WCA) measurements. FTIR and PXRD measurements confirm the formation of CPs whereas the FE-SEM images of suberic acid polymer (SUAP) reveal compact distribution of sphere-like aggregates. WCA measurements showed that the bare MS including CPs coatings on MS up to methylene spacers length m = 4 is hydrophilic in nature; however, the coating of longest methylene spacers length CP (SUAP, m = 6) showed hydrophobic nature with water contact angle of similar to 108.6 degrees. Furthermore, the obtained hydrophobic SUAP CP with polyvinylidene fluoride (PVDF) as binder was coated on MS to study its anticorrosion behavior for the protection of MS. The anticorrosion performance of the developed SUAP coating was investigated by open-circuit potential (OCP) and potentiodynamic polarization techniques. The corrosion rate has been calculated from potentiodynamic polarization curves for the bare MS and SUAP coated MS showed significant improvement in the anticorrosion behavior of the developed SUAP coating.