Effects of biochar nanoparticles on anticorrosive performance of zinc-rich epoxy coatings

Biochar nanoparticles (BCN) derived from spruce wood and wheat straw were prepared, characterized and incorporated into zinc-rich epoxy coatings, with the aim of improving the zinc powder utilization and the anticorrosion performance. Formulations with different BCN and commercial carbon black dosages (0.4 wt%, 0.8 wt% and 1.6 wt%) were compared to a zinc-rich epoxy paint (ZRP) without carbon addition. After immersion and salt spray exposure, coated steel panels were characterized with optical, electrochemical and spectroscopy techniques to evaluate the anticorrosive performance. BCN and carbon black addition enhanced the local electrochemical reactions and the barrier effects were promoted by an increased amount of zinc corrosion products (Zn5(OH)8Cl2 and ZnCO3). The formulation with 0.8 wt% of spruce wood BCN performed equivalently well compared to the ones with carbon black. The degraded area and rust accumulation around the artificial scribe for the formulation with 0.8 wt% of spruce wood BCN were 29.8% and 27.8% less than ZRP, respectively, which is attributed to the good electrical conductivity and high specific surface area of spruce wood char. These results suggest a promising and sustainable option for improving the anticorrosive performance of zinc-rich epoxy coatings by the incorporation of BCN.