Aluminum is anodised both to increase corrosion resistance and to allow dyeing.

 

When exposed to the atmosphere, aluminum forms a passive oxide layer which provides moderate protection against corrosion. In its pure form aluminum self-passivates very effectively, but its alloys, especially 6000 series due to the magnesium content, are far more prone to atmospheric corrosion and therefore benefit from the protective quality of anodising. Aluminum alloy parts are therefore anodized to increase the thickness of this layer for corrosion resistance. Most aluminum aircraft parts including major components are anodized. Anodized aluminum can be found in many consumer products like park benches, childrens outdoor seating, and many other products both for corrosion resistance and the ability to be dyed.

 

Anodized coatings have a much lower thermal conductivity and coefficient of linear expansion than aluminum. As a result, they will crack if exposed to temperatures above 80°C, although they will not peel.[1] Their melting point is 2050°C, much higher than pure aluminum's 658°C

 

Aluminium products offer the following benifits in outdoor applications:

 

• Durability - Long lasting products
• Long lasting - Quality materials
• Will not corrode - Permanent materials
• Smooth, with no sharp edges - Rounded and molded profile
• Easily cleaned - Anodised coating
• Less maintenance - Permanent finish
• No painting required - Permanent coating may be applied
• Does not get hot - Low heat absorption
• Less liability - Difficult to damage and vandalism
• Strong, safe and appealing - Lightweight, strong and attractive
• Low cost