Anti-Corrosion Properties of Tantalum-Based Composite Films Prepared by Atomic Layer Deposition

Reported herein is tantalum (Ta)-based film, including TaN, TaO_x, composite TaO_xN_γ, multilayered TaN/TaO_x-(5:5) and TaN/TaO_x-(10:10), prepared by atomic layer deposition (ALD) technology via adjusting the sub-cycle of TaN and TaO_x films. The influence of different growth parameters on microstructure, crystal form, chemical bonding state and corrosion resistance of Ta-based films was systematically investigated. Representative results include the following: (1) The surface of the Ta-based films prepared by ALD is continuous, dense and smooth, and the root mean square roughness (Rq) of those are TaN: 0.74 nm, TaO_x: 0.69 nm, TaO_xN_γ: 0.55 nm, TaN/TaO_x-5:5: 0.56 nm and TaN/TaO_x-10:10: 0.77 nm. (2) The TaN film presents a polycrystalline structure with good crystallinity, while the incorporation of oxygen significantly inhibits the crystallinity of the film. (3) Electrochemical tests in 3.5 wt.% NaCl solution and neutral salt spray experiments show that ALD deposition of Ta-based films can significantly improve the corrosion resistance of carbon steel substrates. The order of corrosion resistance of different films is TaO_xN_γ film > TaN/TaO_x multilayer film > TaN film. Among them, the TaO_xN_γ film exhibited the most excellent corrosion resistance, with a charge transfer resistance (R_ct) as high as 24.75 Ω·cm² and a corrosion current density (I_corr) as low as 1.20 × 10^-6 A/cm², and no obvious rusting phenomenon was observed on the surface of that film after the 2 h neutral salt spray test.