Durable solutions for steel bridges
How modern corrosion protection systems secure structures cost-efficiently
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.
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.
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.“
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. “
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.“
The advantages of thermal spraying as corrosion protection of steel bridges
Sustainability
Cold process
Highly effective corrosion protection
Self-healing effect
Maintenance-free for up to 100 years
No drying time
Logistics & transportation
Unlimited component dimensions
Versatility of steel types
Reduced downtime
Inventory availability & delivery reliability
UV resistance & paintable
Recycling & reduced waste
Free of microplastics
Immediately paintable
Deepen expertise & ensure quality
Further topics
GRILLO solutions for corrosion protection
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Dr.-Ing. Frank Prenger
