Corrosion Control

What we do

Concrete repairs treat the damage, but not always the cause. Where chlorides or carbonation have reached the reinforcement, the steel just outside a new patch repair can begin to corrode, a problem known as the incipient anode effect. Installing corrosion control at the time of repair protects that steel and extends the life of the repair.

We install galvanic anode and hybrid cathodic protection systems as part of our concrete repair works, and produce the designs for them, from anode type, layout and spacing through to the specification. Because we also carry out the testing that identifies the corrosion risk, one team can take a structure from investigation through to protection.

Galvanic Anodes

Discrete galvanic (sacrificial) anodes are set in drilled holes in the parent concrete around the edge of each repair and connected directly to the cleaned reinforcement. The anode corrodes in preference to the steel, delivering protective current to the reinforcement outside the repair, where the risk of renewed corrosion is greatest.

Anode spacing is set by design to suit the structure, typically between 250mm and 350mm centres. We install PatchGuard anodes, which allow standard bonding primers and repair mortars to be used in the reinstatement.

Hybrid Cathodic Protection

Hybrid systems such as DuoGuard work in two stages. The anodes are first powered by a temporary supply, typically for around a week, which draws chloride towards the anodes and builds a protective alkaline layer at the steel. They are then connected directly to the reinforcement and continue to protect it as galvanic anodes, with no long-term power supply needed.

This makes hybrid systems well suited to chloride contaminated structures such as highway bridges. We are trained in the installation of the DuoGuard hybrid system.

Continuity Testing

An anode only protects the steel it is electrically connected to. We test the continuity of every anode connection with a multimeter before the repair is reinstated. On larger schemes the readings are recorded against the anode layout drawings: at Fort Road Bridge over 1,000 readings were taken, every one within the designer’s limit of 1 ohm.

Investigation & Design

Corrosion control works best when it is specified from good data. Our surveys measure chloride content, carbonation depth, cover and half-cell potential to show where the reinforcement is at risk. From those results we produce the corrosion control design for each structure, including the choice of system, anode layouts and spacing, and the specification for the works.

Corrosion control projects

Fort Road Bridge

Location

Tilbury

Date

March – June 2024

Description

We carried out concrete repairs and installed corrosion control to the north abutment of Fort Road Bridge, a two-span road bridge over the London, Tilbury and Southend railway line.

Deteriorated concrete was removed by hydro-demolition and reinforcement with significant section loss was replaced. We then installed PatchGuard galvanic anodes at 350mm centres across the abutment in four phases.

Every anode connection was tested for electrical continuity, with over 1,000 readings recorded against the anode layout drawings, all within the designer’s limit of 1 ohm. The concrete cover was then reinstated using spray-applied repair mortar.

Travellers Lane Bridge

Location

Hatfield

Date

February – March 2025

Description

We installed a DuoGuard hybrid cathodic protection system at the deck joints of Travellers Lane Bridge, a highway bridge of precast concrete beams in Hertfordshire.

Our team completed installation training for the system ahead of the works, and the anodes were installed over weekend day and night shifts.

DuoGuard anodes are first powered by a temporary supply before being connected to the reinforcement, where they continue to protect the steel as galvanic anodes with no long-term power supply needed.

Kingsmead Viaduct

Location

Hertford

Date

September 2023

Description

We carried out concrete repairs and installed corrosion control within the internal voids of Kingsmead Viaduct. Access was through a manhole in the central reservation, alongside live traffic, with the work inside carried out as a confined space operation.

Defective concrete was removed from the deck surfaces within the voids by hydro-demolition to expose the reinforcement. Electrical continuity was checked with a multimeter before the concrete was reinstated with sprayed concrete.

Boots, Folkestone

Location

Folkestone

Date

June – August 2025

Description

We carried out concrete repairs and installed corrosion control to the exposed concrete edge beams of a four-storey retail and office building, working from scaffold and by rope access.

Defective concrete was broken out and the reinforcement cleaned and primed. PatchGuard galvanic anodes were then installed and connected to the steel, with connections checked using a multimeter, before the repairs were reinstated with hand-placed repair mortar, a fairing coat and an anti-carbonation coating.

The works are covered by a 10-year insurance-backed workmanship guarantee.

Princess Alexandra Hospital

Location

Harlow

Date

April – May 2025

Description

We carried out concrete repairs to the concrete soffit in the basement beneath the main kitchen at Princess Alexandra Hospital, where our earlier survey had found high chloride levels in areas affected by water ingress.

Defective concrete was removed and the reinforcement cleaned, with new reinforcement installed where section loss was severe. PatchGuard galvanic anodes were installed around the perimeter of the repairs and connected to the steel, before a corrosion inhibiting primer, hand-placed repair mortar and an anti-carbonation coating were applied.

The completed works were signed off by the structural engineer.

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