Cathodic protection of the network: stopping corrosion (2026 practical guide)

Understanding corrosion in a network: spotting the risks before the damage

The most common causes: moisture, aggressive soils, stray currents

Persistent moisture, oxygen and coating defects make the winning trio. On a buried network, acidic soil, high in chlorides or sulphates, accelerates the attack on the metal. Stray currents, often linked to DC installations or earthing faults, can "eat away" a pipe within a few months if protection is insufficient.

The signs on site: pitting, leaks, thickness loss, sensitive points

Visible signs: localised pitting, seeping, rust stains, black deposits, or detached sleeving. Sensitive points always recur in the same places: welds, elbows, fittings, wall crossings, material changes. An ultrasonic thickness check and a potential survey (if cathodic protection is present) prevent discovering the problem at the worst moment.

Measuring urgency: criticality, continuity of service, repair costs

Work priority: criticality is assessed based on the fluid, pressure, environment, access, and the impact of a shutdown. A leak on a strategic section often costs more in downtime, repair and collateral damage than a planned intervention. Objective: secure it fast, repair it properly, then monitor.

Cathodic protection: principles, objectives and implementation framework

The basic principle: turning the pipe into a "cathode" to stop the attack

Cathodic protection lowers the potential of the steel so that the pipe behaves as a cathode. Corrosion, which is an anodic reaction, is then strongly slowed down. It complements an external coating. The objective is simple: reduce thickness loss, secure the structure and extend its service life, especially in wet or aggressive soil.

The two approaches: sacrificial anodes or impressed current

Two solutions exist. Sacrificial anodes, often magnesium or zinc, supply a "natural" current. This suits short networks and modest needs. Impressed current uses a power supply and dedicated anodes to deliver an adjustable current. This is the standard route for long pipelines and variable environments. Sizing according to standards is essential.

The essential checks: potential, insulation, electrical continuity

Without checks, there's no lasting protection. You track the pipe-to-soil potential with a reference electrode, check the insulating joints, electrical continuity and equipotential bonds. Regular measurement campaigns detect coating defects, poor insulation and stray currents. Traceability and a maintenance plan make the difference.

Choosing the right cathodic protection for your network

Buried vs submerged networks: constraints and material choices

A buried network is subject to soil resistivity, moisture and stray currents. Magnesium anodes or an impressed-current solution are often preferred if the run is long. In a submerged environment, salinity and water movement point rather towards zinc or aluminium and suitable supports.

Compatibility with coatings: protection + coating working together

Cathodic protection does not replace a good coating. A continuous coating lowers the current requirement and extends the service life. Treat defects (scratches, porosity) and check adhesion to avoid overprotection, which can weaken certain films.

Sizing: measurement points, anode placement, accessibility

Plan for regular, accessible measurement boxes to track potentials with the appropriate reference electrode. Place the anodes where current distributes well, without hindering operation. Good sizing also means simple maintenance over 10 to 20 years.

Installation and monitoring: lasting protection in 2026

Site steps: preparation, connections, continuity test, commissioning

On site, protection is decided from the preparation stage. Cut the power, secure the area, check the support and access. Make clean hydraulic connections (sealing, purging) and compliant electrical connections, then run a continuity test and an earthing check. Finish with commissioning, settings, and a baseline reading (temperature, pressure, regulation parameters).

Maintenance plan: periodic readings, adjustments, anode replacement

A simple plan prevents costly failures. Schedule periodic readings, check for leaks and pressure, and adjust settings as needed. On tanks, monitor the anode's condition and plan its replacement according to water quality and the manufacturer's instructions. Objective: keep protection active and performance steady across the seasons.

2026 traceability: monitoring log, timestamped readings, proof of checks

In 2026, trust comes from the record. Keep a monitoring log with dates, photos, equipment references, and timestamped readings. Add proof of checks (continuity, sealing, commissioning) and maintenance interventions. This is your clear file for warranty, insurance, and to secure inspections over time.

Common mistakes to avoid for truly effective protection

Underestimating stray currents: diagnosis and correction

Stray currents (trams, rails, welding returns) can reverse potentials and accelerate corrosion. Before adding protection, measure on site the potential differences, identify the sources, then correct them. Drainage, earthing, limiting current returns, or adjusting the rectifier.

Forgetting bonds and insulation: weak points at junctions and branches

Protection is often lost at junctions. Flanges, branches, weld repairs, damaged sleeving create unexpected paths. Check every junction, ensure continuity where it's intended and fit insulating joints where it must be broken. Also check cables, connections and measurement boxes.

Confusing cathodic protection with a simple coating: limits and good practice

A coating reduces water ingress and the current required, but it ages and doesn't treat localised defects. Confusing paint with cathodic protection leads to surprises. Combine intelligently: compatible coating, surface preparation, adhesion checks, and settings based on regular measurements.