Abstract
The performance of atmospheric air plasma sprayed bond and ceramic coatings on mild steel was assessed using dc electrochemical methods. Open circuit behaviour and results of potentiodynamic polarisation were studied for the material in contact with carbonate-bicarbonate solutions containing added chloride ions. The oxides Al2O3 and Cr2O3 were applied to bond coatings of NiCr and NiAl. The bond coating oxidation resistance and the deposition parameters determined the propagation and location of corrosion sites. Depending on its degree of porosity, the ceramic coating acted as a diffusion barrier to aggressive ions and water. The effects of post-treatment hipping and superficial laser refusion were also studied. The degradation mechanism is discussed.
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