There are several ways to protect steel structures from corrosion: * **Painting and Coatings:** Applying multiple layers of paint or specialised coatings creates a barrier between the steel and the corrosive elements. * **Galvanising:** This involves coating the steel with a layer of zinc, typically through hot-dipping. Zinc acts as a sacrificial anode, corroding in preference to the steel. * **Electroplating:** Similar to galvanising, but a thin layer of another metal, such as chromium or nickel, is deposited onto the steel surface. * **Metallising:** This is a thermal spray process where molten metal (often zinc or aluminium) is sprayed onto the steel surface. * **Stainless Steel:** Using stainless steel alloys, which naturally contain chromium, provides a high level of corrosion resistance. * **Inhibitors:** Chemical inhibitors can be added to the environment in contact with the steel (e.g., in cooling systems) to reduce the rate of corrosion. * **Cathodic Protection:** This is an electrochemical technique used when the structure is in contact with an electrolyte. It involves making the steel the cathode of an electrochemical cell, either by connecting it to a more easily corroded "sacrificial anode" or by using an "impressed current" system. * **Cladding:** Covering the steel with a more resistant material like concrete or a composite can protect it from the environment. * **Design Considerations:** Good design can minimise areas where water can collect or moisture can be trapped, thereby reducing the risk of corrosion. This includes proper drainage and avoiding crevices. * **Regular Maintenance and Inspection:** Periodically inspecting the structure for signs of corrosion and carrying out necessary repairs, such as repainting or re-coating, is crucial for long-term protection.

Protecting steel structures from corrosion is a topic that often resurfaces only when there's already a problem: rust appears, coatings flake off, elements weaken, and repair costs rise. Yet, in many cases, this can be prevented with simple decisions: with good surface preparation, a correctly chosen protective system and control of operating conditions.

If you want to prevent steel from rusting, choose a protection method that suits the structure's working environment, expected lifespan, and budget. Below you'll find the most important anti-corrosion methods and the key areas where costly mistakes are most often made.

Corrosion protection of steel structures – standard and technical requirements

The anti-corrosion protection of steel structures should not be chosen "by eye". Technical requirements relate, inter alia, to surface preparation, selection of the painting system, coating thickness and quality control of the execution.

It is crucial to determine environmental corrosivity classesin which the structure will work. Different requirements apply to elements inside a hall, and others to structures exposed to weather conditions, moisture, or industrial pollution. At this stage, it’s also decided whether standard paint coatings will suffice, or if protective paint systems with enhanced durability are needed.

Important principle: protection should cover the entire structure, not just the 'visible' parts. Omitting joints, edges, and mounting points is a common cause of accelerated corrosion.

Anti-corrosion protection for steel structures – ISO standard

One of the fundamental points of reference for shell security is PN-EN ISO 12944 concerning the protection of steel structures by painting systems.

In practice, the norm orders:

• environmental corrosivity classes
• Surface preparation requirements
• Coating system selection,
• Minimum requirements for coatings and quality control principles.

The conclusion is simple: the durability of a coating results from the correct application of technology to the environment and the quality of workmanship, not from the "better paint" itself.

Protection of steel structures against corrosion and design and documentation

Effective protection starts in the design. The technical documentation should indicate which safety system is to be used, which materials are permissible, and which parameters must be met.

The project should take into account:

• type of construction and steel elements,
• working environment and corrosivity class,
• cover and performance requirements
• surface preparation
• transport and storage of elements after coating.

A lack of precise records in documentation often leads to errors.: too thin a coating, improper surface preparation, or omission of details. Effect: corrosion appears sooner than expected.

How to protect steel structures from corrosion in practice?

In practice, steel is protected by protective coatings that limit the metal's contact with moisture, oxygen, and aggressive environments. Effectiveness depends on the entire process, not just one product.

The most common reasons why security is not working:

• poor cleaning of steel surfaces
• leaving rust or contamination,
• too thin coating
• omitting critical areas: edges, seams, joints.

Well-executed protection extends the service life of a structure, reduces downtime and repair costs, and protects the load-bearing capacity of elements.

The anti-corrosion protection of steel structures involves a range of methods and materials designed to prevent or slow down the process of steel oxidation, commonly known as rust. This protection is crucial for ensuring the longevity, structural integrity, and aesthetic appearance of steel constructions. **The primary mechanism of corrosion is an electrochemical process.** In the presence of oxygen and an electrolyte (like water or moisture), a chemical reaction occurs where iron atoms lose electrons (oxidation) and other substances gain them (reduction). This results in the formation of iron oxides, which we recognise as rust. Anti-corrosion protection aims to disrupt this electrochemical process by: 1. **Creating a Barrier:** This is the most common approach, where a protective layer is applied to the steel surface to isolate it from the corrosive environment (oxygen and moisture). * **Painting and Coating:** This is the most widely used method. It involves applying multiple layers of specialised paints, epoxies, polyurethanes, or other organic coatings. These coatings provide a physical barrier and often contain anti-corrosive pigments that chemically inhibit the corrosion process. Surface preparation (cleaning, sandblasting) is critical for the adhesion and effectiveness of coatings. * **Galvanisation:** This involves coating the steel with a layer of zinc, typically through a hot-dip process. Zinc is more electrochemically active than iron, meaning it will corrode preferentially, acting as a sacrificial anode. This protects the underlying steel even if the coating is scratched, as the zinc will corrode instead of the steel. * **Metal Spraying (Metallisation):** This involves spraying a molten metal, usually zinc or aluminium, onto the steel surface to create a protective layer. Similar to galvanisation, these metals act as sacrificial anodes. 2. **Altering the Environment:** This involves modifying the surroundings to make them less conducive to corrosion. * **Control of Humidity:** In enclosed spaces, reducing humidity can significantly slow down corrosion. * **Use of Inhibitors:** In certain industrial processes or closed-loop systems, chemical inhibitors can be added to the electrolyte to slow down the corrosion rate. 3. **Electrochemical Protection:** This method uses an external electrical current to alter the electrochemical potential of the steel. * **Cathodic Protection:** This is commonly used for buried pipelines, ships, and offshore structures. It involves either connecting the steel structure to a more easily corroded "sacrificial anode" (like magnesium or zinc blocks) or using an "impressed current system" where an external DC power source forces the steel to become the cathode in an electrochemical cell, thus preventing it from corroding. **Key Considerations for Effective Anti-Corrosion Protection:** * **Surface Preparation:** Thorough cleaning and preparation of the steel surface are paramount. Any mill scale, rust, dirt, or grease will reduce the effectiveness and lifespan of the protective system. * **Application Method:** The correct application of coatings or protective layers is essential. This includes correct thickness, uniform coverage, and proper curing. * **Environmental Exposure:** The type of protective system chosen depends heavily on the intended environment. Steel structures exposed to harsh marine conditions, industrial pollution, or high humidity require more robust protection than those in dry, indoor environments. * **Maintenance and Inspection:** Regular inspection and maintenance of protective coatings are necessary. Small defects can be repaired before they lead to significant corrosion. In summary, anti-corrosion protection for steel structures is a multi-faceted approach that combines physical barriers, chemical treatments, and sometimes electrochemical methods to prevent the degradation of steel due to rust, ensuring the safety and durability of the construction.

Anti-corrosion protection is a technological process that runs from assessing the condition of the structure, through surface preparation, to the application and inspection of coatings.

This is not a one-off "painting of steel" but a set of actions tailored to the structure's geometry and operating conditions.

Anti-corrosion protection of steel structures – process stages

The typical process involves:

• assessment of the technical condition and degree of corrosion
• surface cleaning and preparation
• selection of a protection system
• shell applications
• quality and coating parameter control.

Surface preparation as the basis for corrosion protection

This is the stage where even the best system can be most easily "ruined". Steel surfaces must not be left with rust residues, grease or dust. Sandblasting the steel is often necessary to achieve the correct cleanliness and roughness. If the surface is poorly prepared, the coating will lose adhesion and corrosion will quickly appear.

How to protect steel so it doesn't rust?

Most often Protective coatings are applied in the form of paint systemsselected according to the operating conditions and expected durability. Good protection should guard not only chemically but also mechanically, as damage to the coating is a direct route to corrosion.

Anti-corrosion paint and protective painting systems

In practice, multilayer systems are used, e.g. with a primer layer and a top layer. Depending on the requirements, these can be epoxy or polyurethane coatings, or other solutions adapted to the working environment.

The choice is influenced by, among other things:

• corrosion resistance
• Hardness and resistance to damage,
• Expected lifespan,
• possibility of later maintenance.

Hot-dip galvanising as corrosion protection for steel structures

Hot-dip galvanising is one of the most common methods of anti-corrosion protection for steel components, especially where the structure is to operate in demanding conditions: outdoors, in environments with increased humidity, or in places where long-term durability and reduced maintenance are important. 

It involves immersing a steel element in molten zinc, creating a durable protective layer on the surface.

In practice, galvanisation works in two ways:

• creates a barrier which cuts off steel from moisture and oxygen,
• it provides electrochemical protection, as the zinc "sacrifices itself" at any points of damage, slowing down the corrosion of steel.

However, it must be remembered that galvanising requires appropriate preparation of the structure and the manufacturing technology. Not every structural detail is equally easy to galvanise, and the element's geometry can affect the quality of the coating.

Hot-dip galvanising is also sometimes combined with painting in a so-called duplex system, when even higher anti-corrosion protection and a specific aesthetic effect of steel elements are required.

Protecting steel from corrosion with oil – when does this solution make sense?

Protecting steel from corrosion with oil is mainly effective as temporary protection, for example, during the storage or transport of steel components. Oil limits moisture access to the surface, but it is not a long-term solution and does not replace coating systems.

The rules for transporting and storing steel and the corrosivity of structures

The transport and storage of steel have a real impact on its corrosivity, as it is at this stage that you can "destroy" the effect of surface preparation and subsequent protection. All it takes is dampness, contact with road salt, mud, or prolonged storage in an open space for corrosion to appear on the steel surface. This subsequently reduces the adhesion of coatings and increases the risk that the protection will not be durable.

The biggest problem is the situation where steel elements are stored or transported without protection, and contaminants and moisture settle on the surface. If the steel has already been cleaned, it should not be left "in the field" waiting for further work, because even brief dampness can degrade the surface parameters.

In practice, it's worth sticking to a few rules:

• stack elements on bearers, with clearance from the ground and ensuring ventilation,
• avoid sealing tightly with film without the possibility of moisture evaporation
• to protect components from water, salt and mud during transport, especially in winter,
• protecting critical areas (edges, joints) from chipping and mechanical damage,
• Before painting, remove any dirt acquired during transport and check the condition of the surface.

Properly planned transport and storage minimise the risk of corrosion starting even before protective coatings are applied, or of the coatings being damaged before the structure is put into service.

Steel constructions from ON-Time Solutions

Planning to build a steel structure? At ON-Time Solutions, we design and manufacture steel structures for demanding industries, and we select anti-corrosion protection at the design stage, so that the structure is durable and ready for harsh working conditions.

Consult your project:
Call: +48 512 683 681
office@ontimesolutions.pl

FAQ – Frequently Asked Questions about Corrosion Protection