Chloride attack is the deterioration of reinforced concrete caused by chloride ions penetrating the concrete and breaking down the protective layer around embedded steel reinforcement.
Explanation
Chlorides commonly enter concrete through:
- De-icing salts
- Marine or coastal exposure
- Contaminated aggregates or water
- Industrial environments
Once chlorides reach the reinforcement, they disrupt the passive protective layer created by concrete’s alkalinity. This initiates corrosion, even if carbonation has not occurred.
Chloride-induced corrosion often develops internally before visible damage appears. Over time, expansion from rust formation leads to cracking, delamination, and concrete spalling.
In the UK, chloride attack is frequently seen in car parks, bridges, coastal structures, and heavily trafficked areas exposed to winter salt treatment.
Why It Matters
Chloride contamination can continue to cause corrosion even after local patch repairs.
Accurate diagnosis may require chloride testing and depth profiling. Remedial strategies can include concrete breakout, corrosion treatment, protective coatings, or cathodic protection systems for long-term control.