Fencing made of corten steel is an architectural application. Heterogenous coloring caused by atmospheric conditions and oxide stains is some of the weakness of corten steel. “Some circumstances require a solution to the inherent disadvantages of the Corten steel
Corten steel is characterized by its low maintenance, unlike, for instance, a paint coating. Over time, the surface oxide layer of weathering steels becomes more and more stable, unlike paint finishes, which gradually decompose due to atmospheric agents and thus require frequent maintenance.
One common issue with naked Corten steel is that the oxide is water soluble, particularly in the early stages of oxidation. Consequently, the rainwater that washes the steel surface also drags certain contents of dissolved oxide, which result in reddish or rust stains in the water deposition zones.
Especially on concrete surfaces, these stains are hard to remove. It is a well-known problem that gets softer over time as the patina ages and becomes more stable.
After the oxide has been stabilized, some treatments recommend applying varnish as a third stage. Using this varnish, we will modify the anticorrosion model of Corten steel so that it will behave as painted steel in the future, where the effectiveness of the protection will be determined solely by the capacity of the varnish layer to maintain the water tightness of the structural assembly, i.e. to isolate the steel surface from moisture.
Feature blisters will occur if the varnish layer is damaged or some areas are left unprotected allowing moisture to enter.
Feature blisters will increase progressively until the varnish is detached, chipped off, or exfoliated. This is the usual deteriorating process of any coated metal structure and the same model applies to the varnished Corten steel, with the peculiarity of the presence of a highly hygroscopic patina under the paint layer that will increase the speed of degradation.
In addition to iron and carbon, Cor-Ten steel contains copper, chromium, nickel, phosphorus, silicon, and manganese in small quantities and less than 5% of the total metallurgical composition. Cor-Ten’s strength and corrosion resistance make it such a popular choice. This is all possible because of the steel’s structural composition and the particular distribution and concentration of alloy elements. As a result, they reduce the carbon content, increase load capacity, and above all, provide exceptional corrosion resistance.
In spite of Corten steel’s impressive corrosion resistance, it also has some disadvantages that should be considered before using it
Weakness Of CorTen Steel :
Environmental Limiting Factors
Due to the corrosion effects of steel, areas affected by sea air, heavy rains, humidity, or persistent fog are not ideal places to use Cor-Ten sheet facades.
It is true that surface coatings are formed more quickly and are darker in color in industrial environments than they are in rural settings. Sodium chloride exposure in seaside resorts may slow down the formation of protective coatings. Both cases, however, may result in the coating not adhering perfectly to the metal substrate, resulting in a lack of corrosion protection properties typical of Cor-Ten steel due to the conditions just described.
Uneven Colour Variation
The color of Cor-Ten does not change homogeneously with time, so there is no guarantee of this. This could pose a problem, since, in the event that a facade panel needs to be replaced, it would be rather difficult to trace its matching Cor-Ten color.
Necessity For Constantly Clean Surfaces
The material must always be kept clean, away from mud, grease, oil, paint, cement, mortar, and other substances, in order to minimize contact with agents that might alter the natural oxidation process.
Poor Compatibility With Other Metals
As cladding on facades, Cor-Ten steel is usually installed on substructures, or in any case through metal tracks. It can be risky to join metals with different electrolytic potentials: galvanic corrosion can occur when two metals come into contact with water with different electrolytic potentials.
If weatherproof fasteners cannot be used, nylon spacers should be inserted between the metal types to prevent direct contact between them.
Water And Environmental Control
It should also be noted that, in order to safeguard the finish of the material, the correct design and adequate management of the outflow of rainwater are important. It is important to design all joints and profiles so that rainwater can flow freely without stagnating. Keeping the material well-drained and even out of contact with wet leaves is essential. When atmospheric agents produce oxidation, rust-dirty water can drip onto adjacent surfaces and stain them permanently, or worse, pollute the local aquatic environment.