Chlorides in concrete: causes of corrosion and solutions

Reinforced concrete is designed to ensure strength and durability over time, but certain environmental conditions can compromise the natural protection of the steel reinforcement. Among the main factors contributing to structural deterioration is the presence of chlorides in concrete, one of the most common causes of steel corrosion in building and infrastructure works.

Bridges, multi-storey car parks, industrial structures, prefabricated buildings and structures in marine environments are often exposed to this phenomenon. Understanding how chlorides act and what preventive measures to take is essential for preserving the safety, durability and value of structures.

Chlorides are chemical compounds that can penetrate concrete via water, moisture or exposure to aggressive environments.

The most common sources of chloride contamination include:

• marine or coastal environments;
• brackish water;
• de-icing salts used in winter;
• aggressive industrial atmospheres;
• water ingress in exposed structures.

Under normal conditions, the high alkalinity of concrete naturally protects the steel reinforcement. When the chloride concentration exceeds a certain threshold, this protection is compromised and the corrosion process can begin.

When chlorides reach the reinforcing bars, they break down the passivation film that naturally protects the metal within the concrete.

From that point onwards, localised corrosion can develop, which is often highly aggressive.

The main consequences can be:

• rust formation on the reinforcement;
• increase in volume of the oxidised steel;
• internal stresses in the concrete cover;
• appearance of cracks;
• spalling of the concrete surface;
• loss of structural capacity.

One of the most critical aspects is that chloride corrosion can develop internally over a long period without any obvious signs on the surface.

Chloride contamination primarily affects structures exposed to particularly aggressive environments.

Among the most vulnerable structures are:

• bridges and viaducts;
• multi-storey car parks;
• port facilities;
• industrial prefabricated buildings;
• production facilities;
• buildings in coastal areas;
• structures exposed to de-icing salts.

In these contexts, prevention becomes essential.

Prevention is the most effective strategy for extending the service life of reinforced concrete structures.

When casting new concrete or constructing structural works exposed to harsh environmental conditions, it is possible to protect the reinforcement directly by incorporating specific anti-corrosion systems into the concrete.

An effective technical solution is MCI 2005, designed to protect reinforcement against corrosion caused by chlorides, carbonation and aggressive environmental agents.

This additive is used in:

• prefabrication;
• infrastructure projects;
• car parks;
• bridges;
• industrial projects;
• marine environments.

The use of a migratory additive significantly increases the durability of reinforced concrete.

Even existing structures can be protected using specific surface treatments.

MCI 2020 is a solution designed to penetrate deep into the concrete until it reaches the steel reinforcement, helping to slow down corrosion that has already begun or to prevent it from starting.

This treatment is ideal for:

• balconies;
• facades;
• prefabricated buildings;
• car parks;
• infrastructure exposed to the elements.

In the presence of chlorides, certain signs may indicate that a corrosive process is underway:

• longitudinal cracks along the reinforcement;
• oxidation stains;
• spalling of the concrete cover;
• persistent water ingress;
• localised surface deterioration.

Taking prompt action helps to limit repair costs and preserve structural safety.

For structures exposed to harsh environments, prevention is far less costly than restoration.

Implementing protective measures at an early stage allows you to:

• extend the service life of the structure;
• reduce the need for extraordinary maintenance;
• minimise operational downtime;
• maintain mechanical performance;
• protect the investment in the long term.

The presence of chlorides in concrete is one of the main causes of corrosion in steel reinforcement, particularly in structures exposed to aggressive environments or de-icing salts.

Understanding this phenomenon and implementing specific protective systems makes it possible to prevent structural damage, reduce maintenance costs and increase the durability of structures.

Thanks to the technical solutions developed by Proind, such as MCI 2005 and MCI 2020, it is now possible to effectively protect both new buildings and existing structures.

Contact us to identify the most suitable protection strategy for your structure: whether it is a new construction, maintenance work or a temporary protection requirement, we have the tailor-made solution.