A Study on the High-Temperature Molten Salt Corrosion Resistance of Hot-Dip Aluminum/Carburizing Composite Coating on Ti65 Titanium Alloy

Abstract

This article presents a new method for preparing a coating on Ti65 titanium alloy using a two-step procedure comprising hot-dipped aluminum and solid carburization. The effects of the carburization on the hot-dipped aluminum coating against the presence of a NaCl deposit at 810 °C were systematically studied. In this article, the microstructure, morphology, phase composition of the coating, and corrosion products were investigated using SEM (Scanning Electron Microscopy), EDS (Energy Dispersive Spectrometer), and X-ray diffraction. The results indicated that the corrosion resistance of the hot-dip aluminum/carburizing composite coating was not significantly enhanced with the hot-dip aluminum coating. This can be attributed to the formation of TiC and Ti3AlC after carburization, which promoted the formation of loose and unprotected TiO2 in the coating during molten salt corrosion. In addition, the oxidation of the carbon atom into CO2 led to a high concentration of pores in the coating, creating channels for NaCl to penetrate the coating and accelerate the corrosion rate.