Corrosion Performance of a Novel NiAl-Cu Intermetallic HVOF Protective Coating Part I: Low Temperature Corrosion in 0.5 M H2SO4

In this study the NiAl system macro-alloyed with Cu was used as a protective coating in an Inconel 600 alloy and X52 steel at low temperature for studying the corrosion conditions due to the "dew point corrosion" phenomena which produce sulfuric acid in fuel oil plants boilers. Conventional DC electrochemical test such as polarization curves and linear polarization resistance were compared with corrosion results obtained by the electrochemical noise (EN) technique. The results show that the NiAlCu coating protect well both alloys and is a very good option for against the dew point corrosion. However the steel coated protection do not reach the levels obtained for the coated Inconel 600 alloy, furthermore the coated Inconel 600 alloy seems to resist better the acidic corrosion environment. The EN techniques shows similar results and increase the knowledge of the corrosion of the coated and uncoated alloys showing corrosion mechanisms and performance, as this technique was used to monitor the corrosion of the studied alloys over time. The R-n and R-p values show some discrepancy but have the same corrosion resistant sequence of the alloys under study proving their equivalence. Further deeper analysis was proposed to do in a subsequent paper corresponding to the EN data analysis.