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Painting of steel structures – a way to protect against corrosion

Designing halls and shelters, for industrial purposes, has recently become very popular. No wonder – steel structures are much simpler to prepare and do not require a number of formalities that an investor would have to complete when wanting to erect a traditional building. The strength of the shelters is such that they can create new workplaces or storage areas cheaply. However, be sure to properly protect the external parts-they are mostly made of steel, which is prone to corrosion!

Rust – when and where does it form?

Without proper protection, the steel structure will very quickly become covered with a characteristic tarnish – the alloy is composed largely of iron, which easily transforms into an oxide form when in contact with air and certain substances. This causes rust efflorescence, not only lowering the aesthetic value, but worse, weakening the stability of the structure.

Corrosion is a natural process of transition of pure iron into its original oxide form, so without proper protection even the purest alloy will not resist rust. Steel structural components exposed to the elements are even more vulnerable to the development of defects. For this reason, enhancement products are used – layers of zinc or chrome or special marine paints to protect their surface.

Ways to avoid rust

The very design of steel structures makes it possible to implement certain solutions for securing the raw material – in order to increase its resilience, practical construction and low complexity of elements are relied on. The main point here is that the steel structure should have as few nooks and crannies and spaces as possible into which moisture could enter.

There are also other ways to protect against the effects of rust. These include:

  • the use of corrosion inhibitors, i.e. substances introduced into the corrosive environment that limit its development,
  • The use of electrochemical techniques to increase the resistance of components by creating cathodic protection on their surfaces,
  • Preparation of a protective coating, which can be an anti-corrosion paint for metal, varnish or metallic coating.


Types of anti-corrosion paints and systems

Single-component paints are often used as protection for the metallic coating – these include alkyd and polyvinyl products, which are characterized by a short drying period and are often used to cover standard steel structures, containers, sometimes also as protection for agricultural machinery. The two-component anticorrosion paint has similar properties. Here you can distinguish between epoxy products – fast-drying and well covering, and polyurethane paints with anti-corrosive and decorative properties.

Sometimes products are also used:

  • Silicone – heat-resistant paints for protecting coatings exposed to strong temperature fluctuations,
  • Ethyl silicate – anti-corrosion paints used in the protection of furnaces and pipelines of steel structures,
  • chlorinated urethane products, water-based, marine or polyvinyl acrylic paints.


How to choose an anticorrosive paint system?

Steel structures (sheds, industrial halls or storage areas) are made of different materials, so it is worth first determining what type of surface we are dealing with – this will allow us to choose the right method of protection. To assemble the structure is often used:

  • Black (carbon) steel – in its case, protection is particularly important, since this raw material is considered the most susceptible to corrosion. The best way to protect here is to coat the steel structure with anti-corrosion pigment,
  • Galvanized steel – has been pre-protected already in the alloy clarification process. The intact raw material does not require additional preparations, after the destruction of the coating, it is only necessary to cover the surface with an anti-corrosion primer,
  • Aluminum – a lightweight material, often used in construction. It does not corrode, so the use of paint has only an aesthetic aspect,
  • Cast iron – although it has a high durability, it is exposed to moisture. However, ship paint for rust will help to protect the surface of the structure well.


The way you operate also matters

Painting of steel structures is worth preceding with an analysis of their purpose. The first consideration, especially important when selecting an anti-corrosion coating, is whether it is to cover a component located inside or outside the building. In the latter case, you need to use paints with increased durability.

Vulnerability to mechanical damage and friction is also an important consideration – such structural elements should be protected with epoxy resin or polyurethane-based paints. On the other hand, if you want to paint the inner part of the tank, pay attention to what substance it will be filled with. Some stored liquids may react with the prepared coating and damage its structure.


You need to check the corrosive environment and the shelf life of the coating

Before buying the right paints, it is a good idea to determine the type of corrosive environment. EN ISO 12944-3 distinguishes 6 categories here:

  • C1 – dry interior, very low corrosivity,
  • C2 – moist interior, low corrosivity,
  • C3 – rural and urban outdoor environment, medium corrosivity,
  • C4 – medium salinity industrial and coastal environments,
  • C5 – chemically aggressive environment with very high corrosivity,
  • C6 – very strongly aggressive environment.

In lighter cases, it is usually enough to paint standard steel structures or protect elements with ordinary impregnation, while in more chemically aggressive environments it is necessary to use extended methods of protection – including the selection of properly prepared steel or the appropriate method of joining elements.

  • The required life of the coating is also important. A distinction is made in this category:
  • L – durability of up to 7 years,
  • M-strength from 7-15 years,
  • H – from 15 -25 years,
  • VM – very long shelf life, over 25 years.


Modern solution – marine paints

Recently, high-quality epoxy anti-corrosion primers, or marine paints, have become quite popular. Although they are associated with the shipbuilding industry, they are actually great paints for protecting steel structures, sheds and storage halls.

Marine paints are widely used in coating systems on steel and non-ferrous metals – they effectively protect components from external influences, in particular, insulate the material from moisture.


Sigma marine paints – why is it worth it?

  • For securing a steel hall, C5 system components such as:
  • Sigmacover 280 anti-corrosion primer,
  • Sigmacover 350 thick-coat priming paint,
  • A topcoat of two-component product Sigmadur 520.

The products of this line are often used in the shipbuilding industry, as well as to protect structures prepared from steel or other alloys. Marine paints are known for their excellent adhesion to steel, including galvanized steel and non-ferrous metals. Their appropriate consistency allows for precise preparation of the coating and complete coverage of the component. Sigma marine paints are great for protecting welded and assembly joints and covering the exterior of steel structures. After applying the product, we get a smooth, damage-resistant coating that effectively blocks access to the alloy of the structure. With this protection, steel sheds can resist corrosion for many years!

Paints for painting structures (click)

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