Rust Corrosion

What causes it

• Most materials produced with large levels of energy such as steel and aluminium, will attempt to convert themselves back to their constituent materials on exposure.
• The steel surface will begin to breakdown when water, oxygen, impurities and an electrolyte (this is a liquid that provides some degree of electrical conductivity such as sea water) are present.
• On steel, corrosion can quickly lead to the formation of either red or black products. The red iron oxide form will be the most visible and common.
• For aluminium, the same process occurs except that the corrosion products are white and are not always so obviously visible. Unlike steel however, a layer of corrosion on exposed aluminium will prevent it from corroding any further as the surface is protected. It’s for this reason that aluminium boats and other objects can remain unpainted.

How to prevent it

• Paint correctly to remove one or all of the factors required for corrosion.
• Use correct paint systems below the waterline and use impressed currents and/or sacrificial anodes. See article on electrolysis.

How to treat it

• For simple surface corrosion remove all signs of corrosion and repaint the substrate.
• For more serious corrosion, call in an expert to ensure the source of the corrosion is removed before repainting.
• The use of a sufficiently thick coating of paint will provide a barrier to one or all of the conditions needed for corrosion.