Long-term Hot Corrosion Behavior of Boiler Tube Alloys in Waste-to-Energy Plants

Accelerated corrosion of candidate alloys was induced by metal chlorides/sulfates at 500°C. Results suggest that the corrosivity of the studied metal chlorides increases in the order CaCl₂ < NaCl < KCl < ZnCl₂ < PbCl₂ < FeCl₂. Mechanisms to explain the different impacts of chlorides were proposed. It is believed that materials exposed to chloride salts corrode through vicious cycles, in which a shorter path of the cycle leads to a higher corrosion rate. Experimental results confirmed that FeCl₂, with the shortest path of the corresponding vicious cycle, resulted in the highest corrosion rate. It is also confirmed that the sulfates of Zn and Pb are less corrosive than their chlorides for the alloys tested. A kinetic study on the hot corrosion of T22, Esshete 1250 and Sanicro 28 was carried out under simulated waste-to-energy (WTE) ashes at 500°C for 1000 h. Results from the kinetic study show that T22, Esshete 1250, and Sanicro 28 exhibited comparable performance for short-term exposure; however, the degradation thickness presented a clear trend after the 1000 h exposures in terms of decreasing resistance to corrosion: T22 > Esshete 1250 > Sanicro 28. EDX maps confirmed the role of Ni/Cr for slowing the corrosion kinetics of these three alloys.Applied Science, Faculty ofMaterials Engineering, Department ofReviewedFacultyGraduat