Roasted neem (Azadirachta indica) bark powder/polyaniline (PANI)-epoxy composite coating for anticorrosive application

Composites of roasted neem powder and polyaniline (PANI) were synthesized through chemical oxidative polymerization. The major elemental composition of roasted neem bark powder was carbon, oxygen followed by silicon. These prepared composites were subsequently integrated as fillers in an epoxy-polyamine. The formulations show excellent adhesion on mild steel with a rating of 5B. With the addition of roasted neem bark powder and roasted neem bark powder-PANI composite, the pencil hardness increased to 6H from 4H for blank epoxy. Epoxy roasted neem powder (EN)-4% and EN-PANI 2% formulations showed scratch hardness of 1800 kg. All the coatings showed enhanced mechanical properties as compared to blank epoxy coating, as aromatic PANI hinders the chain moment and roasted neem core provides additional strength. The studied variations show excellent acid, alkali, and solvent resistance. Anticorrosive properties were studied using salt spray and electrochemical impedance spectroscopy (EIS). The highest impedance value in terms of logZ is observed for EN-PANI 4% b1 in the range of 8.6, whereas the lowest is for blank epoxy, i.e. similar to 5 logZ. PANI improves the anticorrosive behaviour by forming an oxide layer on the substrate while roasted neem powder acts as a barrier and hinders the flow of moisture and oxygen to reach the substrate. [GRAPHICS] .