Two distinct Tafel regions are observed in the active region of the anodic polarization curve of iron in ammoniacal carbonate solution. A prepassive layer may form in the Tafel region at the higher overpotentials. A hydrogen oxidation peak is proposed to occur in the lower overpotential Tafel region. Anodic dissolution of iron in both Tafel regions is under mixed surface and diffusion control. The passivation of iron in ammoniacal solution involves charge transfer followed by a rate controlling chemical step. The stability and/or thickness of the passive layer and the Fe(III)/Fe(II) ratio increase with more noble potentials in the passive region.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry