Coating behaviour for materials of industrial waste incinerators and heat exchangers in high temperature corrosive atmospheres

Abstract
A coating obtained by flame spraying (Ni-Al) and an aluminizing type (Sermaloy J) were tested in laboratory and in industrial waste incinerator (substrate : AISI 310S steel). In laboratory tests, the studied parameters were : HCl-content (1 and 3% vol. in air + 0.1% vol. SO₂), temperature (600 and 800 °C) and thermal cycling between 800 and 400 °C. The increasing of the temperature and HCl-content, and also thermal cycling lead to a degradation of the non coated steel and Ni-Al coated specimen behaviours ; as for Sermaloy J, only temperature raising seems to have a detrimental effect (first batch). For the field tests, the specimens were exposed at about 600 °C in flue gases containing about 0.4% vol. HCl and flying ashes (sodium chloride and sulfate) ; the corrosion phenomena are more closed to molten salts interactions than to gaseous corrosion : Ni-Al behaves better compared with Sermaloy J and the non coated steel which are much more attacked than in laboratory. However, Sermaloy J and Ni-Al can lead to a real protection of a steel substrate but the manufacturing conditions have a great influence on the behaviour of the coated specimens.