PORT MAINTENANCE
Extending the life of marine structures How cathodic protection can add decades of service By Carla Neal, Vector Corrosion Technologies
M arine structures are built to withstand some of the harshest conditions on earth. Yet even the strongest steel and reinforced concrete face a relentless enemy: corrosion. Left unchecked, corrosion can lead to costly repairs, operational disruptions, and pre- mature replacement of critical infrastructure. The good news? With the right corrosion protection strategy, the service life of marine structures can often be extended by 20 to 75 years, depending on the design and application of the cathodic protection system. The Tidal Zone: Corrosion’s perfect environment While every part of a marine structure experiences environmental stress, the tidal and splash zones are often the most vulnerable to corrosion. As tides rise, seawater deposits chlorides onto concrete and exposed steel. As the tide recedes, those same surfaces are exposed to oxygen. This continual cycle of wetting, drying, oxygen exposure, and chloride accumulation creates ideal conditions for corrosion to accelerate. Over time, this process weakens structural components, increases maintenance costs, and shortens the life of valuable infrastructure. Understanding how corrosion works Corrosion is an electrochemical process. For it to occur, four components must be present: • An anode – the area where metal corrodes
Over time, chlorides from seawater—or carbon dioxide from the atmosphere—penetrate the concrete. Once these contaminants reach the reinforcing steel, they destroy the passive protective layer and corrosion begins. As steel corrodes, it expands. This expansion creates inter- nal pressure that causes concrete to crack and spall. The cracks then allow even more chlorides and moisture to enter, With the right corrosion protection strategy, the service life of marine structures can often be extended by 20 to 75 years...
• A cathode – the protected portion of the metal • A metallic path – allowing electrons to flow • An electrolyte – enabling ionic movement
The results of environmental stress, tidal and splash zones on concrete.
In marine environments, seawater is an exceptionally effi- cient electrolyte, making corrosion cells easy to establish. Although it has a higher electrical resistance than seawater, concrete also acts as an electrolyte and allows for a corrosion cell to form in steel reinforced concrete. Why reinforced concrete eventually fails Steel reinforcing bars are naturally protected inside con- crete because the concrete’s high alkalinity forms a thin pas-
sive oxide layer on the steel surface. Unfortunately, concrete is porous.
Understanding how corrosion works.
July 2026 — PACIFIC PORTS — 35
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