⚙️ Galvanising is like putting a shiny, protective coat on iron. The zinc layer covers the iron surface, acting as a physical shield that blocks water, oxygen and other corrosive agents from reaching the iron. Because zinc is more reactive than iron, it forms a passive oxide layer that is very stable. The iron underneath stays safe as long as the zinc coating remains intact.
Provides a continuous barrier against moisture.
Prevents direct contact between iron and corrosive species.
Easy to apply by hot-dip or electroplating.
🛡️ When zinc is attached to iron, it becomes the sacrificial anode. In an electrochemical cell, zinc gives up electrons more readily than iron:
\$\ce{Zn -> Zn^{2+} + 2e^-}\$
The electrons flow to the iron, reducing iron ions back to metal:
\$\ce{Fe^{2+} + 2e^- -> Fe}\$
Because zinc corrodes first, the iron stays protected. Think of zinc as a heroic shield that sacrifices itself so the iron can live longer.
• When asked about galvanising, mention both the barrier effect and the sacrificial protection provided by zinc.
• Include the key half‑reactions in LaTeX format.
• Use the analogy of a “protective shield” and a “sacrificial hero” to explain the concepts simply.
• Remember that the zinc coating must remain intact for the protection to work; any cracks expose the iron to corrosion.
| Condition | Effect on Iron |
|---|---|
| Ungalvanised (no zinc) | Rapid corrosion → rust forms quickly. |
| Galvanised (zinc coating) | Corrosion is delayed; zinc corrodes first, protecting iron. |