Hot-dip Galvanizing of Steel

9 October 2025

SealteQ

Steel

Hot-dip galvanizing is an effective way to protect steel against corrosion for a long time. However, in many applications, galvanizing alone is not sufficient. Especially for structural steel that is exposed to weather, wind, or chemical influences for extended periods, additional preservation is crucial to extend its lifespan and limit maintenance costs.

In this article, we explain what hot-dip galvanizing of steel entails, what challenges are involved, what alternatives and combinations are possible – and how SealteQ can help with a sustainable total solution.

Hot-dip galvanizing, also known as immersion galvanizing, is a commonly used surface treatment for steel in which steel is immersed in a liquid zinc bath with a temperature of approximately 450 °C. During this process, a metallic coating of zinc forms on the steel surface, also known as a zinc layer or zinc coating. This layer protects the steel against corrosion, i.e., rust formation, caused by oxidation and atmospheric influences such as moisture, oxygen, and pollution.

The technique offers excellent corrosion protection through cathodic protection: if the zinc layer is damaged, the zinc sacrifices itself to protect the underlying steel. As a result, the construction remains protected for a long time, even with minor damage. Hot-dip galvanizing of steel is widely used in the construction sector, for example in bridge construction, fencing, offshore installations, steel structures, and agricultural machinery.

Although hot-dip galvanized steel offers a high degree of corrosion resistance, it is not sufficient in many situations. For example, consider environments with high atmospheric loads (such as coastal areas), aggressive substances (ammonia, acids), or high aesthetic requirements. In such cases, the zinc coating alone is not sufficient, and additional protection is necessary.

What are the Alternatives, and how Do You Make the Right Choice?

Besides hot-dip galvanizing of steel, there are also other methods to protect steel against rust. Some alternatives include:

Stainless steel (RVS): a type of steel that is naturally corrosion-resistant due to the addition of chromium and nickel. Stainless steel is more expensive and has different mechanical properties.
Wet painting (liquid coating): Suitable for large or complex objects that do not fit in an oven. Can be applied to materials sensitive to high temperatures and is easier to touch up or repair on-site.
Metallizing (thermal spraying): Offers excellent corrosion protection, especially in aggressive environments. Can be combined with other coatings for extra protection.
Fire-resistant coatings: Slow down the heating of steel during a fire, thereby preserving structural integrity longer.
Solvent-free coatings (hot-spray): Fast curing and suitable for applications where solvents are undesirable.
Wrapping tapes (e.g., Stopaq, Kebu): Ideal for underground pipelines and hard-to-reach places. Easy to apply without extensive surface preparation.
Duplex system: Hot-dip galvanizing and powder coating are often combined in a duplex system, where the zinc layer protects the steel against corrosion and the powder coating protects the zinc layer against external influences.

The choice depends on factors such as steel types (carbon steel, structural steel), desired lifespan, corrosion protection, aesthetics, and budget. The type of project also plays a role: what works in bridge construction is not always suitable for agricultural machinery.

SealteQ delivers complete steel preservation, both on location and in our specialized workshops. We take care of the entire process: from surface cleaning to advanced coating techniques.

Our Range of Services

Our service package includes mobile blasting, including dust-free sponge-jet blasting – an efficient and environmentally friendly way to pre-treat surfaces. We also offer metallizing, the application of single- or multi-layer coating systems, and fire-retardant coatings (30, 60, or 90 minutes). Solvent-free coatings with hot-spray equipment, and the application of wrapping tapes such as Stopaq or Kebu are also among our options.

For projects with high corrosion loads, we apply Thermal Sprayed Aluminum (TSA): a self-healing aluminum layer that is ideally suited for applications with minimal maintenance margins. All our activities are checked by NACE-certified specialists and recorded in extensive quality reports with accompanying warranty certificates.

On-site steel preservation

In addition to our permanent facilities in Bergharen and Bergum – equipped with spray halls, spray booths, and blasting booths – we have a complete mobile fleet. This allows us to carry out preservation work at any desired location. Consider mobile blasting units, metallizing equipment, spraying equipment, extraction units (with integrated lighting and communication), screen solutions, and own units. This flexibility enables us to switch quickly and at the same time guarantee a high-quality standard. Thanks to this combination of craftsmanship, technology, and mobility, we offer sustainable protection and unburden clients in sectors such as infrastructure, industry, and civil engineering. Finally, SealteQ also removes chromium 6 from paint layers of structures, so that they no longer pose a risk to the health of people and the environment.

Clients often have many questions and concerns about the application of hot-dip galvanized steel. Below, we answer the most common ones:

What if the Coating Comes Loose or Rust Occurs?

Then there is a good chance that the pre-treatment or coating thickness did not meet the requirements. Adhesion is a critical factor; good pre-treatment (such as blasting, passivation, or anodizing) is essential.

What about environmental regulations, such as the REACH directive?

Hot-dip galvanizing generally complies with the REACH directive, provided that the zinc alloys used are free of prohibited substances. Also, pay attention to waste and emissions during preservation processes.

What are the Standards and Tolerances I Need to Consider?

The most important standard is NEN-EN-ISO 1461. This prescribes requirements for coating thickness, adhesion, and tolerances. ISO 12944 is also often used for coating combinations.

What should I Include in the Design?

Ensure drainage holes, sufficient accessibility for inspection, and space for the preservation company to do its job properly. Without a good design, you run the risk of inadequate preservation.

How Long Does Galvanized and Coated Steel Last?

Depending on the environment and maintenance, up to 50 years or more. Inspection and maintenance are limited, which is in line with sustainable and low-maintenance construction.

SealteQ specializes in the preservation of steel structures, including galvanized steel. Although we do not carry out the hot-dip galvanizing ourselves, we work closely with reliable galvanizing companies. This way, we can offer a complete process: from advice to preservation.

We think along from the initial design, monitor the tolerances, and ensure that the preservation process after galvanizing seamlessly meets the requirements of your project. Through our knowledge of adhesion, coating thickness, and corrosion behavior, we can deliver solutions that contribute to a longer lifespan, lower emissions, and less maintenance in the long term.

Would you like to know what the best approach is for your project? Contact us for a free consultation.

MultiPaint Steel Preservation and MCB coating terminal Arnhem

Preservation of steel structure (5000 m2)

3,000m² steel preservation job Groningen

Commissioned by the construction consortium OV Terminal Arnhem (Ballast Nedam Bouw and BAM Utiliteitsbouw), MultiPaint Staalconservering B.V., in collaboration with MCB from Bergharen—both part of the SealteQ Group—coated the steel structure of the terminal's waiting area.

On behalf of Arendsen Steel from Ulft, the specialists of SealteQ MCB are busy with the preservation of a large steel structure with approximately 5000m2 of material surface.

In Groningen, the specialists from SealteQ Noord are working on an extensive steel conservation project. The project, covering an area of no less than 3,000 m², focuses on conserving the entire steel structure of the building. This requires not only technical expertise but also a meticulous approach that characterizes our team.