Evaluation of synergistic effect of nanozinc/nanoclay additives on the corrosion performance of zinc-rich polyurethane nanocomposite coatings using electrochemical properties and salt spray testing

This research work focuses on the synthesis, characterization and processing of polyurethane/zinc/clay nanocomposites to improve the corrosion performance of zinc-rich coatings. Therefore different percentages of montmorillonite clay nanolayers were added to zinc-rich polyurethane nanocomposites. Ultrasonication process was used to prepare polyurethane/nanozinc/nanoclay composites. Then coatings were applied on steel panels with composition of 10 wt.% nanozinc and 0.5 wt.%, 1 wt.%, 1.5 wt.%, and 2 wt.% nanoclay. TEM was used to analyze the structural characteristics of the samples. The results of the structure analysis revealed the size of nanomaterials. The anticorrosive properties of the nanocomposites were investigated using DC polarization technique, electrochemical impedance spectroscopy (EIS), water absorption and salt spray test. The results of electrochemical tests showed that addition of clay nanolayers improves the corrosion resistance of coatings and the best corrosion performance obtained for the nanocomposite sample with 2 wt.% nanoclay. Also, according to the results of the salt spray test, the sample with 2 wt.% nanoclay showed the least H2O penetration and exfoliation adjacent to the scratches.

► In this study the synergistic effect of clay and zinc nanopigments was analyzed. ► The nanocomposite coatings had a composition of 10 wt.% zinc and 0.5–2 wt.% clay. ► The structure analysis confirmed the proper dispersion in polymer matrix. ► The results of EIS showed the improving of corrosion resistance of coatings. ► The best corrosion performance was obtained for the nanocomposite with 2 wt.% nanoclay.