Exploring corrosion protection properties of alkyd@lanthanide bis-phthalocyanine nanocomposite coatings

Organic coatings have been widely used to protect carbon steel pipelines from external corrosion; however, they often suffer from permeability and weak adhesion. Here we show that synthetic lanthanide bis-phthalocyanine complexes, LnPc(2) (Ln = lanthanide metal, Pc = C(32)H(16)N(8) denotes the phthalocyanine ligand) can be used to form new nanocomposite coatings to provide corrosion protection to the underlying carbon steel pipelines. Electrochemical studies (EIS and potentiodynamic polarization) showed that the incorporation of LnPc(2) compound (PrPc(2), SmPc(2) and HoPc(2)) additives with alkyd coating, leads to a significant increase in the corrosion resistance of carbon steel in 0.5 M HCl solution. The alkyd@LnPc(2) nanocomposite coatings absorb very low water volumes, when compared to the neat alkyd coating. LnPc(2) compounds allowed enhancing the pull-off adhesion of coatings performance from 3.34 MPa to 19.94 MPa. The efficiency of alkyd@HoPc(2) coating appears higher than that of alkyd@PrPc(2) and alkyd@SmPc(2) coatings. The protective properties of alkyd@LnPc(2) coatings were confirmed by SEM, TGA, scratch hardness, impact resistance, bend test and contact angle analysis.