Fighting bridge corrosion: extending service life with MCI

For decades, chloride-induced corrosion has been one of the leading causes of bridge deterioration across coastal, cold-climate, and desert regions. It’s a slow-moving but costly enemy — one that can cut a structure’s design life from 40 years to as little as ten if left unchecked.

As governments and contractors aim to double the lifespan of new bridges, demand is rising for reliable corrosion protection at every stage of design, construction, and maintenance.

Understanding the problem

Corrosion occurs when moisture, oxygen, and chlorides reach embedded steel components such as reinforcement bars or cables. Salt-laden air or de-icing chemicals accelerate this process, eating away at metal, cracking the concrete cover, and eventually leading to spalling. Once corrosion starts, repair costs and disruption can escalate quickly.

Protecting new bridges

Cortec’s Migrating Corrosion Inhibitor (MCI) technology offers a simple, cost-effective approach to prevention. Admixtures such as MCI-2005 can be added directly at the batching plant, forming a molecular barrier around steel reinforcement that delays corrosion onset and slows its rate.

For post-tensioned bridge projects, MCI-309 can be fogged into ducts to protect strands if grouting is delayed. Because it doesn’t leave a greasy residue, grouting can proceed without additional cleaning — saving time on site.

Maintaining existing structures

Corrosion control doesn’t end after construction. Surface-applied inhibitors (SACI) such as MCI-2020 or MCI-2018 migrate through the concrete to protect embedded steel in existing bridges. MCI-2018 combines this action with a silane water repellent, adding extra protection from moisture ingress.

These treatments also help prevent the “ring anode effect” that often occurs after patch repairs by equalising the corrosion potential between new and old concrete. On suspension bridges, MCI vapour technologies can even be introduced through dehumidification systems to protect internal cables.

Building for longevity

Half a century after chloride-induced corrosion became a recognised structural issue, the industry continues to look for better ways to manage it. By integrating MCI technology early in design or applying it as part of a maintenance plan, engineers can extend bridge service life and reduce the need for major repairs.

For case studies and technical details, visit Cortec’s online resource at corteccasehistories.com.