Investigations on highly structured Nanomer® barrier coatings with a combination of organic and inorganic inhibitors for corrosion protection on mild steel

摘要

A novel type of Nanomer® coatings containing a combination of organic and inorganic inhibitorswere investigated with respect to their corrosion protection behavior on mild steel. Differentcombinations of silica platelets, zinc phosphate flakes and organic inhibitors were placed in theepoxy phenolic matrix with overall content up to 20 wt.-%. In particular the synergistic effect ofaddition of different organic inhibitors like benzotriazole [BTA], 2‑methylbenzitrimidazole [2MBI] or4-(4-methylphenyl)-4-oxobutyric acid [4MPO] in combination with the zinc phosphate flakes wasevaluated. The resulting composite mixtures were coated on mild steel (ST1203) using spraycoating. The scanning electron microscopy (SEM) analysis on the morphology of cross-sections isshowing a homogeneous distribution of all used particles in the coatings. The anticorrosionperformance of the sole inhibitors was tested by the linear polarization resistance. The corrosionresistance of the ready coatings was studied by accelerated atmospheric corrosion test supportedby the neutral salt spray test as well as by the electrochemical measurements like electrochemicalimpedance spectroscopy (EIS). The coatings containing the combinations of inhibitors with zincphosphate flakes are exposing improved long-term corrosion protection in comparison to coatingscontaining only the zinc phosphate flakes. Selected samples are keeping the total resistance atthe level of 1 E9 Ω·cm~2 after 6 months of immersion in an 3.5 % NaCl electrolyte. Keywords:flakes; active corrosion protection; zinc phosphate; inhibitors