The corrosion behavior of HVOF Inconel 625 coating in the simulated high temperature and strong corrosive environment

The byproduct gas from yellow phosphorus production contains high concentrations of CO, exhibiting a very high calorific value. However, the corrosive impurities containing in tail gas such as sulfur and phosphorus can lead to rapid corrosion failure of the boiler. The use of high velocity oxygen fuel (HVOF) processed Inconel 625 as coating on the boiler is a highly feasible solution. In this paper, electrochemical corrosion tests and high-temperature acid mist accelerated corrosion tests were conducted to simulate the corrosion performance of yellow phosphorus byproduct gas under environmental conditions. It was found that HVOF Inconel 625 coating revealed low porosity and excellent corrosion resistance. In the corrosive environment simulating yellow phosphorus byproduct gas, significant failure corrosion only occurred on the surface of the samples 72 hours later. The surface corrosion product layer presented a two-layer structure, with high concentrations of Cr2S3, Ni3S2, NiS, and Ni9S8 on the surface, and phosphate based corrosion products on the inner layer. This work preliminarily verified that the Inconel 625 coating prepared by HVOF met the basic requirements for the boilers using byproduct gas as fuel.