Corrosion

By: Pawitra, G.8

Corrosion

Is the gradual destruction of material, usually metals, by chemical reaction with its environment. Corrosion degrades the useful properties of materials and structures including strength, appearance and permeability to liquids and gases.

Fast reactions Can cause explosions. Examples of fast reaction:

a. In car engines, where the fuel is ignited and it burns rapidly producing much heat.

b. Sodium + water. The piece of sodium reacts vigorously with the water, dazzling onto the surface and sometimes burns with a yellow flame.

Slow reactions

Antioxidant is a molecule that inhibits the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Examples of slow reaction:

a. The rotting of food. Your food does not rot in a matter of seconds, does it? It's a chemical reaction, yes!

b. In cooking. The food does not cook that quickly... So people has been devising ways to speed up cooking, such as pressure cooker, ovens, etc.

Rusting

Is a slow reaction which takes place between iron and oxygen. It is an oxidation reaction.

iron + oxygen – iron oxideSteel is used for making girders that support bridges. If the steel is not protected it soon begins to rust.Steel is a compound of iron and carbon. Rust weakens iron and steel.

Factors that speed up rusting

Warmth and salt water speeds up rusting.

Rust prevention

Can be prevented by keeping oxygen away from iron and steel.Steel can be prevented from rusting by mixing it with nickel and chromium to make the metal alloy called stainless steel.

Other metals and the air

Zinc is used to protect iron because it is more reactive with oxygen than iron.Copper is used as a roofing material.Coatings form on some metals when

they are exposed to the air.The surface of bronze, which is an alloy

of tin and copper, develops a thin green film over a long time. This coating is called patina.

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