Colorcoat-Online - Factors affecting durability

Factors affecting durability - external surfaces

All products used for exterior applications are designed to withstand the environment. But all are, to some extent, affected by it.

The main environmental factors which degrade pre-finished steel products are:

Water, oxygen and salts;
Sunlight;
Chemicals and pollutants;
Abrasives such as wind-blown sand and salts.

Water, oxygen and salts

Everyone is familiar with the principle of corrosion in its most advanced state in examples like rusty old nails. But with modern, long-life pre-finished steels, the corrosion process is prevented for decades.

Sunlight

Light energy falling on the earth includes light we can see, from red to blue, and light we can’t, such as Ultraviolet (UV) and infrared. In general, any form of electromagnetic energy can be characterised by its wavelength. The visible region of the electromagnetic radiation spectrum runs from about 400 to 700 nm. UV light falling on the earth has a wavelength between 300 and 380 nm and infrared between 780 and 3000 nm.

Chemicals and pollutants

Chemicals and pollutants can create an aggressive atmosphere which can reduce the performance life of a pre-finished steel product not suited to that environment. They can range from detergents and solvents used for cleaning to typical exterior industrial atmospheres which may contain pollutants such as sulphurous and nitrous gases and also traces of airborne solvents.

Abrasives

Abrasion can be caused by a variety of airborne particles such as wind blown sand and salts. Abrasion resistance has many manifestations, but can be typified by the effect of blowing sand. As in all aspects of durability, not all pre-finished steel products are the same in their resistance to abrasion. Probably the most visual method of assessing this type of robustness is the falling sand method. This specifies the volume of sand which must fall on the painted surface to cause a specified amount of removal of paint from the surface.

Extending durability of pre-finished steels

Ultimately, the degradation of appearance may reach a stage at which it is no longer acceptable. This is not the end of the functional life of the sheet. Over-paint solutions are available for pre-finished steel roof and wall cladding which can restore their appearance and significantly extend the building life. When to repaint will depend on the location and circumstances of the building and its owners.