A railing in a dry interior in Madrid is not the same as a structure on the seafront. The ISO 12944 standard classifies environments according to their corrosivity and is the reference used by engineers and architects to decide how much protection is needed.
Corrosivity categories
- C1 – Very low: heated and dry interiors (offices, homes).
- C2 – Low: rural areas with little pollution; unheated interiors with some condensation (warehouses, sports halls).
- C3 – Medium: moderate urban and industrial environments; low-salinity coastal areas; damp buildings (laundries, breweries).
- C4 – High: industrial and coastal areas with moderate salinity; swimming pools, chemical plants.
- C5 – Very high: industrial environments with high humidity and aggressive atmospheres; high-salinity coastal areas.
- CX – Extreme: offshore, tropical areas with very high salinity.
Durability: L, M, H and VH
The standard also defines how long the system should last until the first major maintenance: L (low, up to 7 years), M (medium, 7–15), H (high, 15–25) and VH (very high, more than 25 years).
What thickness of GALVANOL do I need?
According to the ISO 12944-6 tests in the GALVANOL technical data sheet (applied to grit-blasted steel):
- ≥ 60 µm (1 coat): more than 25 years in C2; 15–25 years in C3.
- ≥ 80 µm (1–2 coats): more than 25 years in C3; 15–25 years in C4.
- ≥ 121 µm (1–2 thick coats): more than 25 years in C4; 15–25 years in C5.
- ≥ 130 µm (2 coats or more): more than 25 years in C5.
To give you an idea: a standard coat applied with a brush or roller leaves about 40 microns dry at around 250 g/m². That is why we recommend 2 coats as standard and 3 coats in aggressive marine or industrial environments. It is not advisable to exceed 200 µm in total.
How to find out which category you are in
Ask yourself three questions: is it outdoors?, is there salt in the air (within a few kilometres of the coast)?, is there industrial pollution, slurry, or chemicals nearby? If you answer yes to two of them, think C4 or C5 and apply 3 coats.
With the surface area and the number of coats, our calculator tells you how many kilos you need. If you want to see real examples, check out our list of projects according to ISO 12944.
Ready to protect your steel?
GALVANOL contains 96% zinc in its dry layer, has been tested in an ENAC-accredited laboratory according to ISO 12944, and complies with ISO 1461 and ASTM A780. We manufacture it in Spain and ship it within 24–72 hours, free of charge to mainland Spain and the Balearic Islands on orders over €50.
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