CorroZone Podcast · 16 Jun 2026
Diffusion Limitation and the Oxygen Reduction Reaction
- Free
- Lecture
- Beginner
- ~22 min
Why oxygen reduction in aerated near-neutral water is controlled by mass transport: the limiting current density i_L = nFDC*/δ and what sets each variable, the Tafel / mixed-control / diffusion-plateau regions of the cathodic curve, reading the resulting Evans diagram, and how deaeration and flow act as mitigation through the limiting current.
Show notes
What you'll learn
- Explain why the rate of the oxygen reduction reaction in near-neutral aerated water is controlled by mass transport rather than electrode kinetics
- State and interpret the limiting current density formula i_L = nFDC*/δ
- Identify the four variables in i_L and describe how each is affected by engineering conditions
- Explain the three regions of a cathodic polarisation curve for ORR: Tafel, mixed control, and diffusion-limited plateau
- Interpret an Evans diagram when the cathodic branch shows a diffusion-limited plateau and identify where the corrosion point falls
- Predict the direction of change in corrosion rate when O₂ concentration, flow velocity, or temperature changes
- Explain how deaeration and flow control act as corrosion mitigation strategies through the limiting current
Who this is for
Anyone beginning their study of corrosion — students, engineers, and technical staff who want a solid foundation in why metals corrode and what can be done about it. No prior background assumed.
What you'll learn
- Explain why the rate of the oxygen reduction reaction in near-neutral aerated water is controlled by mass transport rather than electrode kinetics
- State and interpret the limiting current density formula i_L = nFDC*/δ
- Identify the four variables in i_L and describe how each is affected by engineering conditions
- Explain the three regions of a cathodic polarisation curve for ORR: Tafel, mixed control, and diffusion-limited plateau
- Interpret an Evans diagram when the cathodic branch shows a diffusion-limited plateau and identify where the corrosion point falls
- Predict the direction of change in corrosion rate when O₂ concentration, flow velocity, or temperature changes
- Explain how deaeration and flow control act as corrosion mitigation strategies through the limiting current