材料期刊网

The effectiveness of several thermal-spray coatings for improving the corrosion resistance of a low-alloy steel was evaluated at 650degrees C under two conditions: an oxidizing atmosphere in a fluid catalytic-cracking regenerator of a petrochemical unit and a simulated laboratory atmosphere. The high porosity present in all coatings studied in the present work, inherent to the thermal-spray technique, allowed the penetration of gaseous species from the atmosphere into the substrate, leading to the formation of nonprotective oxides and sulfides, as well as internal oxidation, sulfidation, and nitridation. A protective alumina and/or chromia layer did not form, probably due to the relatively low temperature used in both the real and simulated conditions. Characterization of the phases present in the oxidized layer was carried out by X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy (SEM) with X-ray energy-dispersive analysis (EDS).