Concrete is one of the world’s most widely used construction materials, prized for its durability, strength, and versatility. However, like any other material, it’s prone to deterioration.

One of the primary reasons for the degradation of concrete structures is the corrosion of the embedded steel reinforcements. Corrosion inhibitors are crucial in mitigating this problem, but what types are available, when are they added and where are they best used?

What are Corrosion Inhibitors?

Corrosion inhibitors are chemicals used to prevent or reduce the corrosion rate of metals and alloys when added to a liquid or gas. In the context of concrete, they’re added to protect the embedded steel reinforcements from corroding, thereby enhancing the durability and lifespan of concrete structures.

Benefits of Corrosion Inhibitors in Concrete

  • Extended Service Life: One of the most pronounced benefits of integrating corrosion inhibitors in concrete is the significant extension of the structure’s lifespan. When curtailing the corrosion rate, these inhibitors ensure the concrete remains robust and durable for longer periods. The direct implication is a marked reduction in the frequency of repairs and the overall maintenance costs incurred throughout the structure’s existence.
  • Cost-Effective: On the surface, introducing corrosion inhibitors might add an extra expense. However, the math becomes clear when viewed through the lens of long-term structural health. The upfront cost of incorporating these inhibitors is rapidly offset by the considerable savings garnered from decreased repair and maintenance needs in the future. In essence, it’s a strategic investment for future savings.
  • Improved Structural Integrity: The strength and safety of any structure are paramount. Corrosion can be particularly insidious, silently eroding the reinforcement bars and diminishing the concrete’s load-bearing capacity. Corrosion inhibitors effectively shield the reinforcement, playing a pivotal role in maintaining the structure’s designed integrity and strength.
  • Aesthetic Preservation: Beyond the structural implications, corrosion has aesthetic consequences. It can lead to unsightly discolouration, visible cracks, and other surface blemishes that detract from the structure’s appearance. Using corrosion inhibitors helps mitigate these aesthetic issues, ensuring the structure remains strong and retains its visual appeal for extended periods.

Spotlight on Common Corrosion Inhibitors

To ensure the longevity of concrete structures, let’s focus on four primary corrosion inhibitors widely recognised in the industry.

1. Calcium Nitrite: This inhibitor provides a proactive shield. Its dual action involves forming a protective layer around steel and increasing the chloride threshold necessary to instigate corrosion. Best used in the following applications.

  • Coastal constructions: Given its efficacy in environments with high salt content, calcium nitrate inhibitors are perfect for structures near the sea, where salt spray is a concern.
  • Bridges and highways: These structures are often exposed to de-icing salts in colder climates, making calcium nitrite a suitable choice.
  • Marine facilities: Structures like piers, jetties, and harbours, constantly exposed to salty seawater, benefit from this inhibitor.

2. Organic Alkenyl Dicarboxylic Acid Salt: A environmental champion, this organic inhibitor curtails the electrochemical reactions that foster corrosion. Its adsorptive nature results in a physical barrier that impedes corrosive agents. Best used in the following applications.

  • Environmentally sensitive areas: Its organic nature minimises environmental impact.
  • Urban structures: This inhibitor offers protection and compliance in areas with stringent environmental regulations.
  • Water treatment plants: Such structures often prioritise materials that have minimal environmental repercussions.

3. Anodic Inhibitors: Agents like sodium nitrite focus on the anodic sites of the corrosion cell. Their role involves fostering the formation of oxide films, which act as barriers against rusting. Best used in the following applications.

  • Underground structures: For structures like basements or subway systems, where access for repairs is limited, prevention through these inhibitors is critical.
  • Industrial facilities: Sites exposed to chemicals that could accelerate corrosion.
  • Concrete pipes: These inhibitors can provide an internal protective film, especially those transporting water with impurities.

4. Cathodic Inhibitors: These target the cathodic reaction vital for corrosion to occur. Compounds like zinc oxide are notable members of this group. Best used in the following applications.

  • Car parks and garages: Where carbonation-induced corrosion is a concern due to vehicular exhaust.
  • Heritage structures: Older structures that need a milder, non-aggressive protection method can benefit from cathodic inhibitors.
  • Buildings in high-pollution areas: Where the presence of sulphates and other corrosive agents in the air can hasten rebar corrosion.

When are Corrosion Inhibitors Added to Concrete?

Corrosion inhibitors can be introduced to the concrete at various stages, depending on the type of inhibitor and the specific requirements of the construction project. For complex construction solutions, however, inhibitors are added directly to the concrete mix during the batching process.

These inhibitors become integral to the concrete matrix from the beginning. This strategy is also used with other admixtures, such as water reducers, accelerators, or retarders. It ensures uniform distribution throughout the concrete, providing comprehensive protection to the embedded reinforcement. Examples include Calcium Nitrite and Organic Alkenyl Dicarboxylic Acid Salt, often added at this stage.

Evolving Landscape: What’s Next for Corrosion Inhibitors

Research in this field is ongoing, and SPG is a leading manufacturer and innovator. We’re focused on improving the effectiveness of corrosion inhibitors while lessening our environmental footprint. Three key research areas stand out at the cutting edge of innovation: Smart Corrosion Inhibitors, Nano-Enhanced Inhibitors, and Integrated Materials with our VaporLock 40 Products.

  • Smart Corrosion Inhibitors: The prospect of inhibitors that can self-regulate, adapting to evolving environmental conditions, is particularly exciting. Such materials could “sense” changes and respond accordingly.
  • Nano-Enhanced Inhibitors: Utilising nanotechnology could lead to the creation of corrosion inhibitors that offer pinpoint precision in their application.
  • Integrated Materials: This means that the inhibitors are mixed in, embedded, and intertwined at a molecular or structural level, ensuring a more harmonious and effective protection mechanism than available today.

SPG’s Commitment to Australian Standards

SPG Go Green with VaporLock Products is proud to manufacture corrosion inhibitors that adhere to the highest Australian Standards. Our commitment ensures that our products are efficient and environmentally responsible. We understand the importance of preserving our construction landscape, and our VaporLock products are designed to ensure longevity and durability.

The right corrosion inhibitors can significantly enhance concrete structures’ longevity, safety, and aesthetics. Investing in quality products is an investment in the future of our built environment.