Corrosion Resistance and Hydrophobic Properties of Gradient Coatings Based on Carbon and Alloying Elements

Gradient metal doped diamond-like carbon (Me/ɑ-C(5…20 Hz):Me, where Me–Ti, Cr, Al) coatings were deposited by the synergy of pulse cathode arc and direct-current cathode arc, and C content was adjusted by changing the pulse frequency. The microstructure, composition, surface morphology, the hydrophobicity and corrosion resistance of the coatings were investigated by Ra-man, XPS, SEM, contact angle measurements and potentiodynamic polarization tests, respectively. The XPS method established the formation of carbide com-pounds in the coatings obtained. It is stated that the ratio of carbide/carbon phases in the coating is determined by the type of alloying metal. The values of contact wetting angles for all coatings do not exceed 90°, therefore, the surface is well wetted by a corrosive medium and stays hydrophilic. The analysis of the polarization curves showed that the presence of gradient coatings on the surface leads to the increase in the corrosion resistance of the steel substrate. Cr/ɑ-C(5…20 Hz):Cr coatings are characterized by the highest corrosion resistance. This work is devoted to the studying of influences of type of metal on structure and anti-corrosion property of gradient coatings.