Different locations are grouped into categories depending on the likelihood of corrosion.
In a nutshell:
• Corrosion causes aluminium and steel to deteriorate and decreases the life span of a façade
• The likelihood of corrosion depends on the salt levels in the air which can differ according to location
• ISO Corrosivity Categories provide a guide on how corrosive certain environments are
• There are six categories in total, ranging from ‘Low’ to ‘Very High’
Corrosion is a naturally occurring process that deteriorates materials such as aluminium and steel and can have a large impact on the lifespan of a façade.
The chances of corrosion differ depending on the location therefore knowing the corrosion levels in advance means specifiers can choose the correct coating option for their project. For example, in coastal areas where there are high salt levels, it's advised that aluminium is powder-coated at a thickness of up to 80 microns or anodised to increase its resistance to corrosion.
This is what the ISO Corrosivity Categories can help with as they are a measurement of how much salt is in the air and how quickly corrosion is expected to happen based on where the building is.
Six categories range from ‘Low’ to ‘Very High’ and span across different environments from schools to coastal areas. The table below is based on based on BS EN ISO 12944-2 and BS EN ISO 9223.
| C1 (Very Low) | Heated buildings with clean atmosphere (0ffices, schools, shops) |
| C2 (Low) | Rural areas with little or no pollution |
| C3 (Medium) | Urban and industrial areas with moderate pollution |
| C4 (High) | Industrial and coastal areas with moderate salt exposure |
| C5 (Very High) | Highly polluted industrial zones, coastal/marine environments with high salt levels |
| CX (Extreme) | Extreme industrial areas, offshore areas, and salt spray |
All information was correct at the time of publication, always consult a façade specialist for confirmation.