ČESÁNEK Zdeněk Research and Testing Institute Pilsen


Corrosion resistant coatings must exhibit high density (low porosity), good adhesion to the substrate and of course low penetration of oxides. This paper deals with corrosion resistance comparison of six corrosion resistant coatings, which are frequently used in power plants. The comparison of following coatings is described: two cermet coatings Cr3C2-NiCr and Cr3C2-CoNiCrAlY, one experimental coating TiMoCN-Ni, and three alloy based coatings CoCrWC (Stellite 6), Hastelloy C-276 and NiCrBSi. Each of these six coatings was evaluated using immersion corrosion tests in two selected corrosive aggressive environments. Aqueous solution of 5% H2(SO)4 and artificial seawater were selected as corrosive aggressive environments. All coatings were deposited on W.Nr. 1.0553 carbon steel using thermal spraying technology HP/HVOF (High Pressure/High Velocity Oxygen Fuel). Carbon steel was used as the base material mainly to determine if the open porosity of evaluated coatings does not pose a problem in terms of components surface protection. Evaluation of coating corrosion attack was performed on the surface and in the cross-section of coatings. The evaluation was made before and after corrosion tests using optical and scanning electron microscopy. Furthermore, the amount of corrosion products was examined using mass weight loss/gain during the whole measurement. The corrosion behavior for all investigated coatings was very different. Cr3C2-NiCr cermet coating and alloy based Stellite 6 and Hastelloy C-276 exhibited the highest corrosion resistance in both selected aggressive environments.