Anti-corrosion protection

Corrosion is the process of destruction of materials as a result of external processes. Destructive factors may include, for example, the proximity of sea or fresh water, the presence of chlorides or sulfur compounds in the environment, or simply atmospheric conditions. The product of the corrosion process is rust, i.e. a coating that forms on the metal.

Corrosivity categories are used to determine the degree of corrosive aggressiveness. According to the PN EN ISO 12944-2 standard, this aggressiveness is classified in six degrees for the atmosphere and three degrees for water and soil. In order to correctly select the painting system, it is necessary to determine the conditions in which the structure will operate, and therefore determine the environmental corrosivity category. These categories are as follows: C1 - very low degree of corrosive aggressiveness, internal structure in a heated room with a clean atmosphere (example: shops, offices, school) C2 - low degree of corrosive aggressiveness, external structure in a rural environment or internal structure in an unheated room, where condensation may occur (example: warehouses, sports halls) C3 - medium degree of corrosive aggressiveness, external urban or industrial environment, internal environment with high humidity and air pollution (example: breweries, laundries, dairies) C4 - high degree of corrosive aggressiveness, environment external industrial, coastal areas with medium salinity, internal environment such as chemical plants, swimming pools, repair shipyards C5-I - very high degree of corrosive aggressiveness (industrial) - external environment with high humidity and aggressive atmosphere and internal environment with almost constant condensation and high pollution C5-M - very high degree of corrosive aggressiveness (coastal) - coastal areas, remote from the shore. After appropriately selecting the environmental corrosivity class and determining the minimum required durability of the painting, the appropriate thickness of the paint coating can be selected and the theoretical efficiency of the product can be determined.

Two-component polyurethane paints are characterized by the greatest durability. They provide excellent protection against corrosion and UV radiation. The application of these paints is more difficult due to the need to combine two ingredients and mix them thoroughly. These products should usually be applied at temperatures above 10°C. Such a product is, for example, Telpur S210 primer . Available in 2.2 and 10 kg packages in colors according to the RAL palette. If a small amount of paint is needed, two-component Lowigraf-Pur primer enamel . It is available in 0.88 l and 2.75 l packages in a limited range of colors. In a highly corrosive environment (if the fence is located, for example, next to a busy road or a sidewalk that is sprinkled with salt in winter), we recommend using an additional epoxy primer before applying the polyurethane paint. It can be, for example, FEG-C or Telpox P 100 . If we want simple and quick application, we can choose one-component products, for example Stal-Kor anti-rust primer or Lowigraf polyvinyl paints.

There is no need to wash off the rust remover. Depending on the product selected, you only need to wait a certain time before applying subsequent coats: If you use the Top-Kor , wait 12 hours. Top-Kor can only be overcoated with solvent-based paints. If you use Neodur Metalforce, wait 24 hours. Neodur Metalfroce can be overpainted with both solvent-based and water-based paints. The rust remover applied to iron substrates covered with rust will create a very stable graphite-gray/black layer that will not undergo further oxidation. Applied to smooth, rust-free steel, it will create a colorless varnish coating with good adhesion to the substrate, which will cut off the supply of moisture and oxygen from the air and temporarily protect the substrate against corrosion.

Not all paints can be applied to a freshly galvanized surface. The zinc should be seasoned for about half a year. If it is necessary to repaint such a surface before painting, the structure should be washed with an ammonia solution before painting.

To properly prepare the structure for painting, first of all, the surface must be mechanically cleaned (of old, peeling coatings, loose rust) and degreased. For this purpose, you can use Emulsol RN-1 surface degreasing agent. It is a very efficient product which, after preparing a 2-3% solution (0.5 liters for approx. 16-25 liters of water), is enough to clean from 20 to 50 m2, depending on the degree of dirt. If there is rust on the surface that cannot be removed mechanically, it is best to use a rust remover. If the surface is to be repainted with solvent-based paints, you can use Top-Kor , which is applied with a brush, roller or spray. 1 liter of the preparation is enough to protect approximately 10 m2. Before repainting subsequent layers, wait 12 hours. Another product for derusting surfaces is Neodur Metalforce , which can be used under both solvent-based and water-based paints. After applying the preparation, wait 24 hours before repainting subsequent layers. Depending on the topcoat used and the substrate, it may be necessary to prime the surface with an anti-corrosion primer.

Drying times vary depending on the product and are individual. A very important factor influencing the drying time is the temperature of the substrate and the surroundings, as well as air humidity. In most one-component products, a general rule of thumb is that solvent-based products dry faster than water-based ones. This is because the solvent is more volatile and will evaporate from the surface faster than water. Examples of drying times for single-component paints: Lowicyn (solvent-based polyvinyl paint for galvanized roofs) - 2-3 hours eco-Lowicyn (water-based acrylic paint for galvanized roofs) - 12 hours Telkyd S 200 TM (solvent-based polyvinyl primer enamel) - dust-free after 20 minutes In the case of products two-component paints (epoxies or polyurethanes), the drying time is usually longer because, in addition to physical drying, there is also a chemical reaction between the base and the paint hardener. Drying times for two-component paints "to the touch" (colloquially speaking, when they stop sticking) are 0.5-3 hours, depending on the product. However, please remember that this does not mean that the structure can be transported or repainted after this time. Examples of drying times for two-component paints: Telpur T 300 matt - touch dry 0.5-1 hour - repainting after 24 hours Telpox T 300 - touch dry 1-4 hours - repainting after 24 hours Telpox P 100 - touch dry 0.5-2 hours - repainting after 24 hours There are cases where a long drying time of the coating is an advantage. For example, when spray painting with high-gloss paints, a longer drying time will work to our advantage. During spray painting, the so-called the paint mist, which falls, should blend into the layer of paint already applied to the substrate. If the paint dries too quickly, the falling particles will not be able to connect with it and an unsightly "dust", i.e. tiny dots, will be created. This is why Telpur T 300 (glossy version) has a longer drying time. If short drying time is an important parameter, it is worth paying attention to products where the second layer can be applied using the "wet on wet" method. These are, for example, Telkyd S 200 TM or Telpur S 210 .