Turning Reused Steel into Coastal Protection

Our coasts are on the frontline of climate change. The ARMOUR Project set out to prove that

reused steel can become the backbone of effective, affordable, nature-inspired reef structures — and, in doing so, help catalyse a circular steel economy in the UK.

This project pursued five main objectives:

• Analyse re-used and scrap steel to define potential sources and quantify carbon savings.
• Research corrosion, treatment, and coatings — and evaluate their effects on electrolysis and mineral accretion in laboratory tests measuring rock growth on corroded samples.
• Quantify the impact of corrosion on the strength and brittleness of steel.
• Develop detailed reef design concepts assessing manufacturability, performance, sustainability, and cost.
• Manufacture and install prototype reefs in a controlled test site.

From “Scrap” to Structure

Working with Cleveland Steel and Tubes in North Yorkshire, we identified suitable sources of used steel tubing.

This inspired the creation of a new hyperboloid reef design that can utilise straight steel sections such as rebar or tubular components.

Cleveland Steel fabricated three prototype units, proving that reclaimed steel can be specified, prepared, and assembled for marine-grade applications.

The new reef system was designed for ease of manufacture, transport, and installation — featuring

rapid assembly, flat-pack logistics, and up to 80% lower cost than previous designs.

The climate benefit is immediate: reusing steel in each unit cuts embodied carbon by approximately 45% compared to using new steel.

Pilot Installation

With the support of Exmouth Mussel (UK), we installed and monitored a solar-powered demonstrator, consisting of:

• 2 solar panels
• 6 anodes
• 3 reef units

This pilot provided essential performance and maintenance data under real coastal conditions.

Key Findings

The ARMOUR Project delivered several key findings:

• Rebar from construction sites was found to be an unreliable source of steel for reef manufacture, due to variability in quality and corrosion.
• Corrosion had no negative effect on the electrolysis process or mineral growth. Light surface corrosion was quickly removed through the electrolysis itself.
• Corrosion-induced pitting significantly reduced mechanical performance: a 3 mm steel bar lost around 20% of its deflection strength after one month of corrosion exposure.
• Corroded steel required cleaning before both welding and non-destructive testing (NDT). Ultrasonic NDT was not effective for detecting defects in small spot welds used in the reef design.
• The new reef concept, based on straight sections of pipe or rebar, proved highly effective and affordable. Approximately 80% of the steel in the new design can be used without reprocessing, reducing total reef cost by 50–87.5%, while maintaining the same level of performance.

By demonstrating that reclaimed steel can be safely and effectively reused in marine-grade structures, the ARMOUR Project has opened the door to a circular, low-carbon future for coastal protection. This work shows that sustainable engineering and environmental restoration can — quite literally — share the same backbone.