Corrosion resistance of Cu-Zr(O) N films in a simulated seawater environment

Abstract

Corrosion and antibiofouling protection of maritime transport are important to improve lifetime usage and reduce maintenance costs. Tributyltin (TBT) paint was the most widely used solution, but it was banned due to environmental toxicity in 2008. Multifunctional coatings can be the solution for many current issues, particularly in situations where it is necessary to combine dissimilar properties such as anticorrosion and antibacterial. Zirconium (oxy)nitrides (coatings with great corrosion resistance) doped with copper (proved already to show antibiofouling activity) were obtained by unbalanced magnetron sputtering with a reactive atmosphere to add the anticipated multifunctional characteristics. The properties of obtained films were assessed by SEM, EDS, XRD, AFM, and contact angle measurements. EIS and potentiodynamic polarization tests were performed in NaCl (3.5 % wt.) solution for 168 h to simulate seawater exposure. The results demonstrated that Cu did not form, with Zr(O)N, a crystalline phase. Moreover, Cu incorporation promotes voids among column boundaries of ZrON films, directly influencing their roughness, surface energy, porosity index, and wettability. Regarding corrosion resistance, the inclusion of Cu worsens the Zr(O)N chemical stability against seawater. The obtained results demonstrated the incapability of Cu-Zr(O)N films to be applied as unique coatings to avoid biofouling under seawater exposure due to copper addition.