Microstructure and flow accelerated corrosion resistance of Cr coatings electrodeposited in a trivalent chromium bath

Abstract In this study, Cr coatings were electrodeposited on carbon steel substrates by a trivalent Cr salt. The microstructure of the Cr coatings and their flow accelerated corrosion (FAC) resistance in simulated secondary circuit environments (10 MPa and 150 °C) of nuclear power plants were investigated. The results showed that the as-deposited coating was amorphous and crack-free. Annealing at 200 °C resulted in the decrease of Cr (OH)3 and the increase of Cr and Cr2O3 on the coating surface, which improved the corrosion resistance of the coating. The subsequent FAC test showed that the Cr coatings significantly improved the FAC resistance of the carbon steel substrate. The coating annealed at 200 °C exhibited better FAC resistance. The Cr-rich oxide film formed on the coatings was mainly Cr2O3, with a small amount of Cr and CrO2. Due to the galvanic effects caused by pinhole defects, abnormally grown annular deposits formed on the coating surface.