Chemistry
Explainer
Why Mining Equipment Rusts: Electrochemistry
Rust is a tiny galvanic cell running on your steel.
Quick check · tap an answer to continue
Lesson notes
Key points
- On wet iron, some regions act as anodes where Fe is oxidised to Fe²⁺, releasing electrons into the metal.
- Those electrons reduce dissolved oxygen elsewhere, and Fe²⁺ is further oxidised to hydrated iron(III) oxide, which we call rust.
- Sacrificial protection attaches a more active metal like zinc or magnesium, which becomes the anode and corrodes instead of the iron.
- This is why galvanised roofing sheets and buried pipelines use zinc coatings or attached anodes.
Takeaway: A more active metal sacrifices itself to keep iron cathodic.
Quick check: Why does zinc protect iron from corrosion?
- Zinc is oxidised first
- Zinc blocks all oxygen
- Zinc reduces Fe²⁺ to rust
Zinc has a lower E°, so it acts as the anode and corrodes instead.
Anodic siteRust formationSacrificial anodeGalvanising
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