Corrosion resistance of niobium carbide coatings produced on AISI 1045 steel via thermo-reactive diffusion deposition

Niobium carbide coatings were deposited on AISI 1045 low alloy steel via the thermo-reactive deposition/diffusion technique (TRD). The influence of the percentage of the ferroalloy on the corrosion resistance of each coating was evaluated. The corrosion resistance of the niobium carbide coatings was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in a solution of 3.0% NaCl. The microstructure was characterized via X-ray diffraction (XRD), and the morphology was characterized by means of scanning electron microscopy (SEM). Chemical analysis of the layers was done through Energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results show that the thickness of the carbide coatings does not significantly change with an increasing amount of ferroalloy. Carbide coatings improved the corrosion resistance of the substrates; however, the corrosion resistance of these layers decreased after 24 h of being exposed to the saline solution used, due to the porosity of the coatings and the roughness of the coating-substrate interface. For the most part, the results of the tests of corrosion resistance were not affected by the percentage of ferroalloy in the salt bath.