Corrosion Resistant Polypyrrole/Flyash Composite Coatings Designed for Mild Steel Substrate

Polypyrrole-flyash (PPy-flyash) composite was synthesized by chemical oxidative emulsion polymerization of pyrrole monomer using FeCl3 as an oxidant. The synthesized composite was loaded in epoxy resin and subsequently coated on mild steel substrate using powder coating technique. XRD and FTIR analyses of the synthesized composite show the interaction between polypyrrole and flyash. SEM micrograph shows the embedded flyash particles in polypyrrole matrix. TGA thermograms show good thermal stability of the PPy-flyash composite as compared to neat polypyrrole. TGA thermograms of the coatings (epoxy alone and epoxy with different wt% loading of PPy-flyash composite) show appreciable increase in the thermal degradation temperatures of the coatings with PPy-flyash composite. Corrosion studies in 3.5% NaCl solution suggest significantly high corrosion protection efficiency (%P.E.) and high pore resistance (Rpore) for the epoxy coating with 2.0wt% loading of PPy-flyash composite (PF2). The EIS data obtained for the coatings exposed to 3.5% NaCl solution for 30 days show a superior corrosion resistance offered by the specimen PF2. The enhanced corrosion resistance of the coatings is due to the synergistic interaction between polypyrrole and flyash in the composite. Here, polypyrrole provides anodic protection to the steel substrate, whereas, flyash particles reinforce the integrity of the coating under corrosive conditions.