ANODIC ELECTRODEPOSITION OF Mn-Co-O SPINEL COATINGS ON STAINLESS STEEL SUBSTRATES

摘要

Crack-free, Co-rich nanocrystalline Mn-Co-O coatings have been successfully electrodeposited on ferritic stainless steel substrates from aqueous solutions at temperatures above 70 deg C. The coating chemistry can be manipulated by adjusting the deposition parameters, including solution temperature, metal ion concentration and current density. The effects of deposition parameters on coating morphology have also been investigated. Electron microscopy analysis has revealed that as-deposited Mn-Co-O coatings are composed of nanocrystalline oxide grains with a metastable face center cubic (FCC) structure. This metastable FCC phase transforms into a stable MnCo_2O_4 phase (Fd3m) when annealed at 800 deg C. After long term oxidation, the entire oxide scale is predominantly MnCr_2O_4 containing Co and Fe.