Metals that do not corrode easily generally either do not contain iron, which forms rust (iron oxide), or they form protective oxide layers that prevent further corrosion.
Key Metals That Resist Corrosion:
- Aluminum: It forms a thin, tough layer of aluminum oxide on its surface that protects against further corrosion, even though it reacts readily with oxygen initially. This oxide layer acts as a shield from oxygen and water.
- Stainless Steel: Contains at least 11-18% chromium, which quickly forms a chromium oxide protective layer that prevents rust. The addition of elements like nickel enhances corrosion resistance further.
- Galvanized Steel: Steel coated with zinc, which forms a sacrificial protective layer of zinc oxide to prevent rusting of the underlying steel.
- Copper, Bronze, Brass (Red Metals): These don’t rust because they contain little or no iron. Copper oxidizes to form a green patina, which protects the metal beneath. Bronze and brass, which are copper alloys, are also corrosion-resistant.
- Precious Metals (Gold, Platinum, Silver): These metals do not rust because they do not contain iron and are extremely non-reactive. Gold and platinum do not tarnish or corrode easily; silver is also resistant though it can tarnish.
- Titanium: Known for excellent resistance to corrosion in many environments due to a stable oxide layer, though it is more expensive.
Summary Table
Metal/Alloy| Corrosion Resistance Mechanism| Notes
---|---|---
Aluminum| Protective oxide layer| Lightweight, common in aircraft
Stainless Steel| Chromium oxide protective film| Contains iron but rust-
resistant
Galvanized Steel| Zinc coating sacrificial layer| Zinc oxidizes instead of
iron
Copper, Bronze, Brass| Oxidation forms protective patina| No iron, patina
sometimes green
Gold, Platinum, Silver| Highly non-reactive pure metals| Do not rust, silver
can tarnish
Titanium| Stable protective oxide layer| Highly corrosion-resistant but costly
These metals either avoid rust by lacking iron entirely or form thin oxide or patina layers that shield them from further corrosion.
