Evaluation of the anti-corrosion effect of clay based nanopigments modified with organic azole compounds

In this study, sodium montmorillonite clay (Na+-MMT) nanoparticles were surface modified by azole corrosion inhibitors such as 2-mercaptobenzothiazole (MBT) and 2-mercaptobenzimidazole (MBI) through ionic exchange reaction and used as anti-corrosion nanopigments inside epoxy resin. Small angle x-ray scattering (SAXS) and transmission electron microscope (TEM) tests were used to evaluate the distribution of hybrid nanopigments within the matrix of coating and the structural morphology of the compounds was investigated by scanning electron microscopy (SEM) test. Electrochemical impedance spectroscopy (EIS) and salt spray were also implemented to study the corrosion behavior of nano coatings in the corrosive environment of 3.5% sodium chloride solution. Additionally, contact angle measurement was used to evaluate the levels of hydrophilicity and hydrophobicity of steel surfaces coated with and without clay compounds optimized with azole compounds. The results indicated that epoxy coating containing 3 wt. % of MMT+MBT nanopigment, compared to epoxy coating containing 3 wt. % MMT+MBI and pure epoxy coating had higher anti-corrosion performance after 60 days of immersion in the above-mentioned corrosive environment and presence of this nanopigment led to an increase of the level of hydrophobicity in the related surface.