Introduction
As it has improved resistance to corrosion, it is also called Weatherproof Steel
It is a new material whose colour changes continuously during the oxidation process due to light and atmospheric conditions.
In the initial stage of corrosion, a well-adhered impermeable oxide layer is formed, which hinders any additional oxygen diffusion into the basic metal and prevents internal corrosion.
Structures made of this steel do not need painting, which makes it appropriate for the manufacture of containers, electric towers, metallic structures for buildings, warehouses, coverings, covers, bridges, all kinds of fences, sculptures, urban furniture, etc.
Environmental influences
The degree of exposure has great influence on the protective layer’s formation. If placed in an area exposed directly to rain, sun and wind, the oxide layer will appear more quickly than if the steel is protected. In the latter case, the oxide tends to be rougher, less dense and less homogeneous.
The frequent changes in humidity and dryness favour the acceleration of the weatherproof process. The atmospheric pollution may also have negative effects, which is why in moderate industrial environments this type of steel has a rapid self-correction process and acquires darker shades, while in rural environments the self-protection process is slower and the oxide has generally lighter shades.
In acid environments the protection process takes place more slowly, but the steel may be used satisfactorily.
Not recommended in the following environments:
- Atmospheres that contain chemical vapors or concentrated industrial corrosive agents.
- Places subject to sprayings of salted water or steam containing salt.
- Continuously immersed in water, buried in the ground or in bridges surrounded by water polluted with defrosting salts dripping through seals, open joint and dilation joints.
- In direct contact with wooden covers.
- In structures exposed to humidity for long periods of time.
In these cases the use of this steel is not recommended unprotected or uncoated, as the oxide will not form appropriately.
Protective coatings
Generally, weatherproof steel is used unprotected and uncoated.
Nevertheless, in areas with a high level of humidity, immersed or buried elements, elements built or fixed in concrete, in the ground or gravel, it is recommended to apply a high grade antioxidant primer coating on the clean surface.
On overlapped surfaces, running water could penetrate in the joints and produce corrosion due to the action of capillarity, which is why protection is needed.
The prime coating can be similar to the ones used for carbon steel and applied up to approximately 10 cm above the built-in part.