In this paper, the corrosion behaviour of thermal sprayed and diffusion‐coated materials are compared. The result of the high temperature corrosion test shows that the layers with NiCr applied by atmospheric plasma spraying (APS) and high velocity oxy fuel flame spraying (HVOF) are more resistant than the layers with NiCrBSi and Cr3C2/ NiCr. Furthermore, the layer with NiCr on 15 Mo 3 is more resistant than that on 13 CrMo 44 as base material. The corrosion behaviour of Al, Cr, and Cr/Si diffusion‐coated materials on 13 CrMo 44‐ are better than those same diffusion coatings on 15 Mo 3‐surfaces. In particular, the Cr diffusion‐coated materials show the highest corrosion resistances in this work. Also, the diffusion‐coated materials have higher resistances than thermal sprayed materials in HCl‐H2O‐O2‐N2‐atmosphere.

The aim of this work is to investigate the corrosion behaviour of superheater materials below deposited ashes in biomass combusting atmospheres. The materials were exposed in three different settings (without deposits, with filter ash and with cyclone ash). Exposure tests were carried out with variation of water and HCl content for 360 h at 535uC. The HCl addition led to higher mass losses of materials than those without HCl addition. The rate of mass loss is proportional to the deposition aggressiveness and water content in the HCl containing atmospheres. NiCr rich superalloys are more resistant than austenitic and ferritic steels.