Fabrication, characterization and efficient surface protection mechanism of poly(trans-cinnamaldehyde) electropolymerized coatings for EH36 steel in simulated seawater

Heterogeneous poly(trans-cinnamaldehyde) (PTCA) coatings were electropolymerized on EH36 steel surface in ethanolic electrolyte for corrosion retardation toward the simulated seawater (SSW). The deposited coating was confirmed by morphology observation and wettability. A compact PTCA layer was fabricated with the water content of 0.3% and polymerization time of 600 s. The polymerized mechanism for PTCA was proposed through bonding analysis of coated steel. Open circuit potential, potentiodynamic polarization, electrochemical impedance spectroscopy and surface analyses evidenced the superior protection performance of PTCA-coated steel in SSW for the decreased corrosion current density, increased charge transfer resistance and topography durability. Electrolyte penetration and partial reduction of PTCA during long-term immersion slightly impaired the anticorrosion efficiency in the aspects of barrier effect and anodic protection. Synergistic analyses of electrochemical frequency modulation clearly distinguished the anodic protection as the dominant factor for the conducting PTCA coating in the long-term protection for steel substrate in SSW.