2.19: Understand How the Rusting of Iron May be Prevented By: Barrier Methods, Galvanising, Sacrificial protection

RUST: Chemical reaction between Iron, Water and Oxygen to form Iron (III) Oxide

PREVENTION OF RUST

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1. BARRIER METHODS:
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• Rust can be prevented by coating Iron with barriers that prevent the it from coming into contact with Water and Oxygen (with Metals above Iron in the Reactivity Series)
• However, If the coating is washed away or scratched, the Iron is once again exposed to Water and Oxygen and will rust

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COMMON BARRIER METHODS
GREASE	OIL
PAINT	PLASTIC

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2. GALVANISING / SACRIFICIAL PROTECTION:

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• Rusting of Iron can be prevented by using the Reactivity Series
• Galvanising is when the Iron is coated with a Layer of Zinc
• If the coating is damaged or scratched, the Iron is still protected from rusting as Zinc is more reactive than Iron, therefore reacting with Oxygen and Water to corrode instead of the Iron

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    Example: Sacrificial Anode

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    Zinc Blocks Attached to the Hull of Ships so they will Corrode instead of the Hull