Corrosion-Erosion Effect on TiN/TiAlN Multilayers

The goal of this work is to study electrochemical behavior under corrosion-erosion conditions for [TiN/TiAlN]_n multilayer coatings with bilayer number (n) of 2, 6, 12, and 24 and/or bilayer period (Λ) of 1500, 500, 250, 150, and 125 nm deposited by a magnetron sputtering technique on Si (100) and AISI 1045 steel substrates. The Ti-N and Ti-Al-N structures for multilayer coatings were evaluated via x-ray diffraction analysis. Silica particles were used as the abrasive material in corrosion-erosion tests within the 0.5 M H₂SO₄ solution at impact angles of 30° and 90° over the surface. The electrochemical characterization was carried out using the polarization resistance technique (Tafel) to observe changes in corrosion rates as a function of the bilayer number (n) or bilayer period (Λ) and impact angle. Corrosion rate values of 359 mpy of uncoated steel substrate and 103 mpy for substrate coated with n = 24 (Λ = 125 nm) under an impact angle of 30° were found. On the other hand, with an impact angle of 90° the corrosion rate exhibited 646 mpy on uncoated steel substrate and 210 mpy for substrate coated with n = 24 (Λ = 125 nm). This behavior was related to the curves of mass loss for both coated samples and the surface damage was analyzed via SEM images for the two different impact angles. These results indicate that TiN/TiAlN multilayer coatings deposited on AISI 1045 steel are a practical solution for applications in erosive-corrosive environments.