Q-Carbon as a Corrosion-Resistant Coating

A newly discovered quenched form of carbon, widely known as Q-carbon, thin films are synthesized by the direct conversion of the amorphous carbon layer using the nanosecond pulsed laser annealing technique, and its corrosion-resistant properties, that is, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy technique, are investigated. The unique microstructure and the existence of defects (sp(2) content) in sp(3)-rich Q-carbon are highly desirable for efficient corrosion-resistant performance. The sp(3) percentage of the as-grown Q-carbon is measured to be similar to 80.5% from the D and G peaks of the Raman and C-1S X-ray photoelectron spectrum. The anti-corrosion properties with inhibition durability of Q-carbon thin films are systematically investigated in various concentrations of Na2SO4 solutions, and the corrosion potential, corrosion current, and corrosion rate of Q-carbon are determined to be -253 V, 30.1 x 10(-5) A/cm(2), and 0.00528, respectively, for 1 M Na2SO4 solution. Both series and contact resistance decrease from 5498.6 and 821.1 Omega to 698.8 and 124.3 Omega with an increase of Na2SO4 concentration from 0.1 to 1 M, respectively. The small shift of PDP curves toward more negative potential, the shrinkage of the radius of semicircular arcs in the Nyquist plot (Z '' vs Z '), and negligible loss in corrosion resistance (similar to 78%) are observed for Q-carbon thin film at the immersion time up to 48 h. The unique sp(2)-sp(3) ratio, shorter bond length, compact atomic arrangement, and minimum porosity, along with the high adhesion strength, due to the ultrafast solid-liquid-solid growth route, of Q-carbon thin film on the substrate signify it as a better alternative compared to the existing corrosion-resistant materials.