Citation: Czupry ´ nski, A.; Adamiec, J.; Adamiak, M.; ˙ Zuk, M.; Kˇ ríž, A.; Mele, C.; Kciuk, M. High-Temperature Corrosion of Flame-Sprayed Power Boiler Components with Nickel Alloy Powders. Materials 2023, 16, 1658. https://doi.org/10.3390/ma16041658 Academic Editor: Luigi Calabrese Received: 15 January 2023 Revised: 7 February 2023 Accepted: 14 February 2023 Published: 16 February 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Article High-Temperature Corrosion of Flame-Sprayed Power Boiler Components with Nickel Alloy Powders Artur Czupry ´ nski 1, * , Janusz Adamiec 2 , Marcin Adamiak 3 , Marcin ˙ Zuk 1 , Antonin Kˇ ríž 4 , Claudio Mele 5 and Monika Kciuk 6 1 Department of Welding, Silesian University of Technology, Konarskiego Street 18A, 44-100 Gliwice, Poland 2 Department of Metallurgy and Recycling, Silesian University of Technology, Krasi´ nskiego Street 8, 40-019 Katowice, Poland 3 MaterialsResearch Laboratory, Silesian University of Technology, Konarskiego Street 18A, 44-100 Gliwice, Poland 4 Faculty of Mechanical Engineering, Institute of Technology and Materials, Jan Evangelista Purkynˇ e University in Ústí nad Labem, Pasteurova Street 1, 400 96 Ústí nad Labem, Czech Republic 5 Department of Engineering for Innovation, University of Salento, via per Monteroni, 73100 Lecce, Italy 6 Department of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego Street 18A, 44-100 Gliwice, Poland * Correspondence: artur.czuprynski@polsl.pl Abstract: The development trends in the energy sector clearly indicate an increase in the share of biomass and alternative fuels fed for combustion in power boilers, which results in the imposition of many unfavourable factors and a demanding working environment. During the operation of the energy system, this means a sharp increase in corrosion of the gas-tight pipe walls and coils by the destructive action of chlorine and sulphur. Implementing advanced surface protection in addition to the selection of materials of better quality and resistance to difficult working conditions would significantly reduce their wear by high temperature corrosion. Thermally sprayed coatings offer a great opportunity to protect machine components and energy systems against corrosion, erosion, impact load and abrasive wear. This article presents the test results of high-temperature corrosion resistance of coatings made with Ni-Cr-B-Si and Ni-B-Si alloy powders on a boiler steel substrate. Samples with sprayed coatings were exposed to an atmosphere with a composition of N 2 + 9% O 2 + 0.08% SO 2 + 0.15% HCl at 800 ◦ C for 250, 500, 750 and 1000 h. Tests results of coatings made of Ni-Cr-B-Si alloys subjected to the influence of a corrosive environment showed the formation of a layer of scale on the surface, composed mainly of Cr 2 O 3 oxide, which was a passive layer, reducing the rate of corrosion. Coatings sprayed with Ni-B-Si alloys showed significantly lower corrosion resistance. It was found that the developed technology of subsonic flame spraying with powders of the Ni-Cr-B-Si type allows the production of coatings compliant with the requirements of the energy industry, which allows their use as anti-corrosion protection on boiler elements intended for waste disposal and biomass combustion. Keywords: flame powder spray process; coating; nickel alloy; high temperature corrosion; sheet pile walls; power boiler 1. Introduction High costs of energy produced from energy resources (natural gas, crude oil, fossil coals) and the need to protect the natural environment more and more often encourage world economies to use renewable energy sources obtained from wind, sunlight or water. Biomass is a natural energy resource, which, due to its origin, is divided into: wood biomass from trees and shrubs; green biomass from plants with non-lignified stems and whose above-ground part dies after the cultivation period; fruit biomass from plant parts containing seeds; and a mixture resulting from the deliberate mixing of biofuels [1]. The Materials 2023, 16, 1658. https://doi.org/10.3390/ma16041658 https://www.mdpi.com/journal/materials