Pitting Corrosion in Reinforcing Steel: What is it and How Does it Occur?

Pitting corrosion in steel reinforcement poses a hidden threat to the structural integrity of concrete buildings, often going unnoticed until significant damage has occurred. Understanding how factors like chloride ingress and carbonation contribute to this issue is crucial for taking preventive measures and ensuring the longevity of your structures. Discover how a professional building inspection can safeguard against these risks and provide peace of mind.

Pitting corrosion is a severe form of localized corrosion that occurs on steel reinforcement in concrete. Unlike general rust formation, where corrosion spreads over a large area, pitting corrosion manifests as small but deep "pits" or holes in the steel. This form of corrosion can go unnoticed until it is too late, and therefore poses a significant risk to the structural integrity of concrete structures.

How does pitting corrosion occur?

Pitting corrosion in reinforced steel usually occurs when the protective passive layer on the steel is compromised. This layer is normally maintained by the high pH of the concrete. However, several factors can damage this protective layer:

Chloride ingress
One of the main causes of pitting corrosion is the presence of chlorides, often from road salt or seawater. Chlorides can penetrate the concrete and accumulate around the reinforcement. When a certain threshold value is exceeded, the passive layer breaks down locally, leading to pitting.
Carbonation
This is a chemical process in which carbon dioxide from the air reacts with calcium hydroxide in the concrete, causing the pH value to drop. This causes the steel to lose its protection and can lead to corrosion.
Local damage to the concrete
Cracks, poorly compacted concrete or insufficient cover can allow moisture and harmful substances to reach the reinforcement more easily, leading to local corrosion.

Why is pitting corrosion dangerous?

Pitting corrosion is particularly treacherous because it eats deep into the steel without always being visible on the surface. This can significantly reduce the cross-section of the reinforcement, seriously compromising the strength and durability of a structure. In the worst cases, this can lead to cracking, concrete spalling, or even structural failure.

Prevention and maintenance

To prevent or limit pitting corrosion, there are several measures that can be taken:

Use of corrosion-resistant steel or coatings.
Ensure sufficient concrete cover and a low water-cement ratio during construction.
High-quality concrete finish and protection against the ingress of harmful substances.
Regular inspections.

Do you suspect damage to the structure? Have it inspected!

Pitting corrosion often occurs unnoticed and can lead to serious damage. Do you have doubts about the condition of your concrete structure or suspect corrosion? Then have a professional building inspection performed by Homekeur BV .

🔍 Our experienced inspectors will map potential damage and provide you with a clear overview of the building's condition. This way, you'll avoid unpleasant surprises and know exactly what to expect.

Schedule a building inspection directly at Homekeur BV

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The cost of a building inspection (up to 250 m²) is only €489 including VAT. We'll conduct a comprehensive building inspection and you'll receive a building report. Do you have any questions? We're happy to help and can schedule an appointment with an expert inspector right away if you wish!

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