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What Causes Metal To Corrode?

The sight of corroded metal will be a common occurrence for many people – you go outside to ride your bike and notice a red-brown rust on the frame after leaving it out in the rain; you walk past your beloved old care only to see the body has started to become rusted out after years of disuse. But what actually causes metal to corrode?

Basically, corrosion is an electrochemical process that actually causes some metals to be broken down. Corrosion commonly occurs to anode metals when they come into contact with an electrolyte (such as water, which conducts electrodes), oxygen and a cathode (a substance that accepts electrons). A metal’s electrons will flow through the electrolyte and into the cathode, causing the item to wear away (or corrode). If you add salt to the water, the process of corrosion in your item will be sped up substantially.

The most common form of corrosion is rust – it forms when iron (an anode metal) is combined with oxygen and water (an electrolyte) and a red-brown rust is created (a cathode). Other forms of corrosion in metal include the greening of copper and the tarnishing of brass.

Not all metals, however, are subject to corrosion. Anodes (such as iron, aluminium, brass, copper, bronze and so on) will corrode because of the electrochemical process outline above – but this can be prevented if the proper precautions are taken. Then there are other metals (such as gold and platinum) that are completely resistant to corrosion because moisture and oxygen have no affect on them.