What is a sealer and what is it used for?

A varnish is a transparent coating specially designed to be applied to the surface of Corten steel, a material widely used in architecture, art and landscape design. The main function of this coating is to protect Corten steel against corrosion while preserving its unique aesthetic appearance.

The varnish acts as a transparent barrier that prevents the formation of rust stains on other surfaces and slows down the oxidation process of the steel itself. It thus maintains the original appearance of Corten steel, its characteristic texture and color while providing increased protection against environmental elements.

In summary, a varnish for Corten steel is an essential element in extending the life and visual appeal of this unique material, ensuring that it retains its distinctive character while resisting corrosion. It is commonly used in various architectural and artistic projects to preserve the aesthetic integrity of Corten steel while protecting it from the ravages of time.


Why does Corten steel need varnishing?

Corten steel, also known as weathering steel, is a material that naturally forms a protective rust layer when exposed to atmospheric elements. This outer rust layer provides some protection against corrosion, making Corten steel an attractive material for many applications, including architecture, art and landscape design.

However, there are situations where Corten steel needs to be varnished. The main reason is to preserve the aesthetic appearance of the steel while preventing excessive corrosion. Corten steel's natural rust layer can sometimes stain surrounding surfaces, such as sidewalks or the walls of a building. Additionally, in particularly aggressive or humid environments, rust may progress more quickly than desired, which can compromise the durability and appearance of the material.

By applying a varnish to Corten steel, a transparent protective barrier is created between the material and the humidity in the air. This varnish prevents the formation of rust stains on adjacent surfaces and slows down the oxidation process of the steel, thus maintaining its original appearance. In summary, Corten steel varnishing aims to combine the rustic beauty of this material with enhanced protection against corrosion, ensuring its longevity and visual appeal in various applications.

Does varnish change the appearance of Corten steel?

Varnish applied to Corten steel may slightly change its appearance, although these changes are usually minimal. In general, the varnish is designed to be transparent and therefore preserves the characteristic color and texture of Corten steel.

However, certain factors can influence the appearance of varnished Corten steel. First, varnish can add a slight shine to the surface of the steel, which may be more or less noticeable depending on the type of varnish used. Some varnishes may give a slightly smoother appearance to the steel, while others may be more matte.

In addition, over time and in response to environmental conditions, the varnish may undergo natural degradation. This may result in a slight alteration in the appearance of the material, although this usually takes some time.

Overall, the visual impact of varnish on Corten steel is generally considered minor compared to the importance of protecting against corrosion and preserving the overall aesthetic appearance of the material. The choice of varnish type can also influence the final appearance, so it is advisable to select varnish based on the specific aesthetic preferences of the project.

How to prepare the surface of Corten steel before applying the varnish?

Proper preparation of the Corten steel surface before applying the varnish is essential to ensure correct adhesion of the varnish and effective protection against corrosion. Here are the key steps in surface preparation:

Deep Cleaning: First of all, it is crucial to clean the surface of Corten steel thoroughly to remove dirt, dust, grease, loose rust and other contaminants. Use mild detergent, water and a nylon brush or cloth to thoroughly clean. Make sure the surface is completely clean and dry before proceeding to the next step.
Removal of excessive rust: If the Corten steel surface shows excessive rust or stains, use a mild abrasive like a wire brush or fine-grit sandpaper to remove these imperfections. The goal is to create a uniform, smooth surface.
Degreasing: If traces of grease or oil are present, use a suitable degreaser to remove these substances. Make sure the surface is completely clean and free of any degreaser residue.
Removal of dust residue: After cleaning, make sure to remove any traces of dust or particles fines of the surface. You can use a clean, dry cloth or compressed air for this step.
Applying varnish: Once the Corten steel surface is clean and ready, you can apply varnish according to the manufacturer's recommendations. Be sure to follow the specific instructions for the polish you have chosen in regarding room temperature, drying time between coats, and number of coats needed.