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Corrosion Solutions

Corrosion protection of steel bridges

Steel bridges in Germany need better corrosion protection. Thermal spraying is the proven and sustainable solution.

Durable solutions for steel bridges

How modern corrosion protection systems secure structures cost-efficiently

Corrosion protection of steel bridges is essential for planning, new construction, and infrastructure maintenance. Many steel structures are already damaged by weather conditions, de-icing salts, and outdated corrosion protection systems. Traditional paint coatings are reaching their limits – with short protection cycles, high maintenance requirements, and environmental drawbacks. Thermal spraying with zinc or zinc-aluminium offers a proven, standards-compliant alternative with protection durations of up to 100 years – internationally established and a technology with high potential for Germany as well.

State of German infrastructure: Corrosion protection as a challenge

High investment needs – especially for steel bridges

According to the Federal Highway Research Institute (BASt), around 60% of road bridges in Germany are in need of rehabilitation. The situation is particularly serious for steel bridges on the motorway network: 48% of these structures are already in a condition that requires urgent repairs. An additional 23% of the surface area is classified as particularly critical based on risk assessment.

Germany is lagging behind in the corrosion protection of steel bridges

The use of thermal spray galvanizing to combat corrosion on steel bridges has a long international track record of success. Steel bridges have been protected with thermal spray coatings worldwide since the 1950s. The first projects were carried out in the United States and the United Kingdom. In Norway, the road authority has mandated thermal spray galvanizing for all bridges in coastal environments since the 1960s. The Benelux countries have also been successfully applying the method to road and railway bridges since the early 2000s.

In Germany, thermal spray galvanizing has not yet been fully integrated into official regulations. However, projects like the Grevenhofsluice Bridge demonstrate the enormous potential of this proven method for protecting steel structures against corrosion.

Paint coatings as the German standard – with high follow-up costs

Paint-based protection systems are still considered standard in Germany – despite their limited durability.
In practice, this means that many steel bridges require complete refurbishment approximately every 33 years – a complex, costly, and resource-intensive process. In addition, these systems pose significant environmental concerns: they contain VOC-based solvents, release microplastics, and are non-recyclable. Despite these shortcomings, current German regulations continue to rely on the seemingly simple solution of “more paint layers” – instead of adopting long-lasting corrosion protection systems for steel structures.

A recent life cycle study conducted by the Karlsruhe Institute of Technology (KIT) on behalf of the International Zinc Association (IZA) shows: Thermally sprayed zinc systems significantly reduce life cycle costs, lower CO₂ emissions, and extend protection periods to up to 100 years – all without toxic solvents or microplastics.

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How thermal spraying protects bridges long term

Corrosion protection coating using thermal spraying

Thermal spraying is a proven and standards-compliant solution for the corrosion protection of steel structures. In this process, metallic wire – usually zinc or zinc-aluminium – is melted in an electric arc and sprayed directly onto prepared steel surfaces. The resulting corrosion protection coating adheres mechanically, provides long-term rust protection, and is suitable for a wide range of structural forms.

Unlike paint-based coatings, thermal spraying is applied on-site without the need for immersion baths – even on complex or hard-to-reach steel components. Even thin-walled or delicate steel parts can be coated without thermal distortion.

Thanks to the cathodic protection mechanism, zinc continues to provide corrosion protection even when the surface is damaged – a clear advantage over conventional paint-based systems. While paint coatings typically need to be completely renewed every 33 years, a thermally sprayed zinc-aluminum coating can offer protection for up to 100 years. This reduces costs, minimizes maintenance cycles, and improves environmental performance: thermal spray systems emit less CO₂, generate no microplastic waste, and are fully recyclable.

In countries like Norway, the UK, and the US, thermal spraying has long been established as the standard – both for refurbishing steel bridges and in new construction. Germany should follow this path consistently – for durable, sustainable, and cost-effective corrosion protection of steel.

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Thermal spraying in international bridge applications

Steel bridges in Norway: Corrosion protection for extreme conditions

With over 2,000 steel bridges along its rugged coastline, Norway faces unique challenges in corrosion protection. Thermal spraying using zinc duplex systems has proven to be an effective solution—delivering service lives of over 50 years, even in harsh marine splash zones.

Zandhazen bridge: 100 years of corrosion protection with zinc-aluminium

At the Zandhazen bridge in the Netherlands, a thermally sprayed coating made of 85% zinc and 15% aluminium reliably protects the steel structure against corrosion. The system was chosen to significantly reduce maintenance, environmental impact, and life cycle costs over the planned service life of more than 100 years.

Memorial Bridge: Long-lasting protection through zinc metallization

After 90 years in operation, the Memorial Bridge in New Hampshire had to be replaced — severe corrosion from road salt and the marine environment had caused major damage to its load-bearing elements. The new structure was coated with thermally sprayed zinc, chosen for its excellent adhesion, low risk of transport damage, and long-term durability with minimal maintenance requirements.

Expert opinions on thermal spraying

The only option

„In norway, all the steel bridges are coated with the combination of thermal sprayed zinc and paint. You could use only the thermal sprayed zinc in many cases, but that would give you a dull grey surface, so the architects like to have some color. They have used different colors on the bridge to get a beautiful appearance.“

Ole Knudson, Senior Scientist, SINTEF

Significantly cheaper

„The main reason for using thermal sprayed zinc ist that it’s much cheaper during the lifetime of a bridge. Maintenance will be less complicated, has less pollution an will be cheaper. “

Leon Linssen, BEng, Specialist materials, NACE Certified Coating Inspector Level 3, Dekra

The adhesion is incredible

„So the adhesion on the coating onto the steel is unbelievable. They fabricated, they shipped, they erected. All these massive truss pieces – and there was no damage from shipping, which is unheard of. So, you don’t have to go back and touch up the bridge once it’s erected.“

Jerry Zoller, P.E. Project Engineer Bridge Design, New Hampshire Department of Transportation

The advantages of thermal spraying as corrosion protection of steel bridges

Sustainability

Thermal spraying does not require environmentally harmful chemicals or solvent-based components. Compared to conventional paint coatings, it offers a sustainable solution for the corrosion protection of steel structures and significantly reduces environmental impact.

Cold process

During thermal spraying, the component is exposed to only minimal thermal stress. The process preserves the material properties of the steel bridge and protects the surface efficiently – especially when compared to heat-intensive methods such as hot-dip galvanizing.

Highly effective corrosion protection

The use of high-quality zinc or zinc-aluminum alloys in thermal spraying creates extremely durable protective coatings. These coatings perform reliably even under high mechanical stress and in aggressive environments – significantly more long-lasting than conventional paint coatings.

Self-healing effect

Thanks to the cathodic protection mechanism, the zinc layer continues to protect even when the surface is mechanically damaged. This significantly extends the service life of the corrosion protection system – a clear advantage over conventional paint coatings.

Maintenance-free for up to 100 years

Thermally sprayed coatings can achieve protection durations of up to 100 years without the need for regular maintenance intervals. This drastically reduces life cycle costs – a crucial factor in infrastructure projects.

No drying time

Unlike paint systems, thermally sprayed zinc coatings do not require drying phases. Components can be processed or assembled immediately – ideal for tight schedules and complex construction workflows.

Logistics & transportation

Unlike hot-dip galvanizing, thermal spraying eliminates the need for time-consuming transport to galvanizing plants. The zinc coating is applied directly on-site – whether in the workshop or on the construction site. This not only saves time but also simplifies logistics and improves the CO₂ balance.

Unlimited component dimensions

Thermal spraying is suitable for steel components of any size – regardless of length, weight, or geometry. Unlike hot-dip galvanizing, it has no size limitations caused by immersion baths.

Versatility of steel types

Almost all common types of steel can be protected with thermally sprayed coatings. Even high-strength or sensitive steel grades, for which hot-dip galvanizing is problematic, can be treated without issue.

Reduced downtime

Since no drying or curing times are required, downtime in the production process is significantly reduced. Thermal spraying enables fast coating and further processing – especially advantageous in maintenance applications.

Inventory availability & delivery reliability

Components that have been thermally sprayed can be stored or shipped immediately – with no waiting time for drying or post-treatment. This increases planning reliability and delivery performance.

UV resistance & paintable

The finished coating is UV-stable and provides an ideal base for topcoats, coloring, or markings. The system can be painted over immediately – no time-consuming pre-treatment required.

Recycling & reduced waste

Zinc and zinc-aluminium coatings applied by thermal spraying are fully recyclable. Unlike many paint-based systems, they produce hardly any residues or hazardous waste – a clear advantage in terms of sustainability and circular economy.

Free of microplastics

Thermal spraying uses no polymer-based components. The coating is free from microplastics, significantly reducing environmental risks – especially when compared to solvent-based paint coatings.

Immediately paintable

The thermally sprayed surface is ready for use immediately after application. It can be coated without delay or intermediate treatment – saving time and streamlining workflows in the workshop, on the construction site, or in production.
Training & quality control

Deepen expertise & ensure quality

Whether you want to deepen your knowledge of thermal spraying in bridge construction or gain official certification – GRILLO is here to support you. Our training courses provide hands-on expertise on applications, standards, and technical fundamentals. We also recommend the official SLV certification as proof of your qualification in the field of thermal spray coatings.

Further topics

GRILLO solutions for corrosion protection

GRILLOs corrosion protection solutions offer tailored solutions for various applications, including anode protection, protection of reinforced concrete, and corrosion protection for steel objects such as bridges. Find your suitable solution!

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Talk to us today about the benefits of this highly effective and sustainable application technology.

Dr.-Ing. Frank Prenger

+49 203 5557-422

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