Aluminum composite powder as an additive in epoxy coatings for enhancement of corrosion protection of carbon steel

Electrochemical impedance spectroscopy (EIS) and potentiometric polarization (Tafel) tests were utilized to investigate the corrosion protection efficiency of epoxy (EP) composite coatings reinforced with aluminum powder additives deposited on carbon steel substrate. Different aluminum powders including pure aluminum (Al) and aluminum composites powders containing alumina (Al₂O₃) and carbon nanotubes (CNTs) were used as an additive filler. Various aluminum composite powders containing 2 wt.% of each CNTs and Al₂O₃ nanoparticle were synthesized using ball milling and then added into EP coating at concentration of 1 wt.%. It was found that the incorporation of formulated additive fillers improves the corrosion resistance of neat EP coating owing to enhanced barrier properties of EP composite coatings. It was also found that the barrier property of Al/CNT/Al₂O₃ additive is more significant than other additives owing to reduced particle size and certain shapes of particles as it further reduces the transport paths for penetration of corrosive environment through the coating and greatly prevents possible reactions at metal substrate/coating interface. Moreover, EP-Al/CNT/Al₂O₃ maintained one-time constant characteristic and showed the highest impedence and stability over the whole exposure time. In addition, the presence of these additives strengthens the coating, leading to further improvement of barrier property of the coating.