Duplex Al-Based Thermal Spray Coatings for Corrosion Protection in High Temperature RefineryApplications
Adriana da Cunha Rocha, Fernando Rizzo, Chaoliu Zeng
Materials Research
abstract:The application of thermal spray coatings has been effective in preventing corrosion of steel and iron products. It has been used in a wide range of applications spreading from the petroleum to the food industry. In this work, the performance and effectiveness of a two-layered aluminum-based thermal spray coating applied to anASTMA387 G11 steel was evaluated. The coating structure was comprised of an innerAl-Fe-Cr layer and an outer layer of aluminum. Coated samples were tested in the reactor zone of a fluid catalytic cracking unit (FCCU) of a petrochemical plant for 2.5 years. The reactor zone temperature was about 793 K (520 C) and the environment was a mixed gas containing sulfur, oxygen and carbon. Laboratory-scale tests were also conducted on the coated samples in order to gain a better understanding of the corrosive effect of the gaseous species present in the FCCU atmosphere. Porosity present in the thermal spray coatings allowed the penetration of the atmosphere corrodents, which instigated intergranular corrosion of the steel substrate. The presence of an innerAl-Fe-Cr layer did not prevent coating spallation, which further contributed to the internal corrosion process.
keywords:aluminum coatings; High temperature corrosion; Thermal spray coatings; mixed-gas environments; petrochemical industry
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