Aluminum dihydric tripolyphosphate/polypyrrole-functionalized graphene oxide waterborne epoxy composite coatings for impermeability and corrosion protection performance of metals

A new attractive waterborne epoxy (WEP) coating based on aluminum dihydric tripolyphosphate/polypyrrole/graphene oxide (ADTP-GO-PPy) hybrids was first proposed for the mild steel protection in 3.5% NaCl solution. ADTP-GO-PPy hybrids were synthesized using in situ polymerized GO-PPy as a precursor and anchoring lamellar structure of ADTP on the surface of GO-PPy nanosheets with the coupling agent 3-aminopropyl triethoxysilane (ASi). This induced the superiority improvement in the dispersion ability of ADTP-GO-PPy hybrids in WEP matrix due to significant increase of interspacing from 0.83 to 1.70 nm. Additionally, after decoration by lamellar particles of ADTP, the GO-PPy sheet surface was covered by many lamellar particles of ADTP owing to hydrolysis and condensation reactions between ASi and oxygen containing groups of GO-PPy. Hybrid coating showed clear superiority in improving the anticorrosion property, which can be reflected by the morphologies of the rust layers beneath WEP coating. The superior corrosion protection performance of hybrid coating was attributed to the excellent barrier ability of GO nanosheets, self-healing of PPy film, and layer structure of ADTP.