Electrochemical corrosion of metals (Fe–Cu, Fe–Zn, Fe–Sn) and sacrificial protection
ChemistryElectrochemistryAges 17–18Virtual lab
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Electrochemistry
An iron bar is placed in contact with another metal in NaCl solution, distilled water, dilute acid or dry air: the metal with the lower electrode potential becomes the anode and corrodes, electrons flow to the cathode where O₂ (or H⁺) is reduced, and rust builds up. The mass-loss-over-time graph keeps the previous run for comparison: attaching Zn protects the Fe (the Zn dissolves instead), attaching Cu makes the Fe corrode faster, and a strong electrolyte with dissolved O₂ speeds up corrosion.
Lesson: Metal corrosion – electrochemical corrosion and corrosion protection
What it shows
Electrochemical corrosion occurs when two different metals touch in an electrolyte, forming a galvanic cell. The metal with the lower standard electrode potential becomes the anode and dissolves, while dissolved oxygen or H⁺ ions are reduced at the cathode. For iron, the Fe²⁺ ions formed go on to give hydrated iron(III) oxide, or rust. The same model explains sacrificial protection by zinc on galvanised steel and ship hulls, why scratched tinplate rusts faster than bare iron, and why seawater and oxygen speed corrosion while dry air almost stops it.
How to use
Start with Fe alone in NaCl solution and let the mass-loss graph build up. Press Reset (keep old curve), change the Material and compare the new curve with the old one: iron joined with copper, scratched tinplate, scratched galvanized iron. Then keep the Material fixed and change the Environment or untick Dissolved O₂ present. The anode and cathode labels show which metal is losing electrons.
Parameters you can change
- Material Fe alone, Fe joined with Cu, Tinplate (Sn-coated Fe), scratched, Galvanized iron (Zn-coated Fe), scratched / sacrificial Zn
- Environment NaCl solution (seawater), Distilled water, Dilute HCl solution, Dry air
- Dissolved O₂ present
- Simulation speed 0.5–3 ×
Questions to explore
- In scratched galvanized iron, why does zinc corrode instead of iron, while tin makes exposed iron corrode faster?
- How does the corrosion rate of iron in NaCl solution change when there is no dissolved O₂?
- What are the anode and cathode half-equations for iron joined with copper in seawater?
