The Influence of Protective Coatings on High-Temperature Corrosion under Biomass Ash Deposits

The presented research determined the performance of the protective coatings against the corrosion process under biomass and refuse-derived fuel (RDF) ash deposits. High-temperature corrosion tests were performed on steel grades intended for use in the fabrication of pressure parts working in elevated temperatures such as superheaters in power boilers. Two steel grades were investigated, P235GH and 16Mo3, and two protective coatings were applied, Inconel 625 and Alloy 310. The samples were sourced from the industrial boiler manufacturing company. The samples were exposed to two ashes originating from biofuels and one ash originating from RDF for comparison, all collected from Polish heat plants and power plants. Exposures were carried out in an oxidizing atmosphere for a maximum time of 504 h. The test temperatures of 480, 520, and 580 °C simulated superheater conditions of biofuel- and waste-fired power boilers. The corrosion kinetics were determined by weight change measurements conducted after 24, 168, and 504 h of the exposure. Regardless of the exposure temperature and the type of ash under which the samples were investigated, the use of 2.0 mm thick protective coatings resulted in smaller increases in the weight of the tested coupons which proves that alloy coatings give measurable results and are good remedies for chlorine-induced corrosion.