Whilst you might know that corrosion inhibiting admixtures protect concrete and steel reinforcement, understanding exactly how they do this makes it much easier to select the right one for your project.

So, let’s take a look at how corrosion inhibitor admixtures for concrete structures prevent reinforcement corrosion: understanding corrosion, types of admixtures, mechanisms of protection, and benefits of investing in admixtures.

What is Concrete Corrosion?

Concrete corrosion is primarily the deterioration of the steel reinforcement that’s placed within the concrete to increase its tensile strength, reduce thermal expansion, and provide support during cracking. This corrosion is caused by chemical reactions between the steel reinforcement and various environmental elements; corrosion significantly impacts the structural strength of the finished concrete structure.

Types of Corrosion Inhibitor Admixtures For Concrete

Corrosion inhibitor admixtures for concrete are categorised into inorganic, organic, and green corrosion inhibiting admixtures.

  • Inorganic Inhibitors: These corrosion inhibitor concrete admixtures include sodium nitrite and calcium nitrite that form a protective oxide layer on the steel, shielding it from corrosive elements.
  • Organic Inhibitors: These types of corrosion inhibitors in concrete include certain amine and ester compounds that produce a hydrophobic layer on the steel. They effectively repel water and chloride ions, which is particularly useful in high moisture and chloride environments.
  • Green Inhibitors: These inhibitors are derived from natural, environmentally friendly sources and provide effective corrosion protection with a minimal environmental footprint.

Corrosion Inhibitor Concrete Admixtures – Mechanisms of Protection

Corrosion inhibiting concrete admixtures function through three different mechanisms: anodic, cathodic, and mixed mechanisms.

Anodic Protection Mechanism – Type of Inhibitor: Inorganic

As an example, calcium nitrite is an inorganic corrosion inhibiting admixture and functions by forming a passive film on the steel’s surface. This film acts as a barrier against oxygen and other corrosive elements, preventing oxidation and subsequent corrosion of the steel reinforcement within the concrete structure.

Cathodic Protection Mechanism – Type of Inhibitor: Inorganic

As an example, lithium nitrate is a corrosion inhibitor admixture for concrete that’s classified as inorganic and plays a crucial role in slowing down the cathodic reaction on the steel’s surface. Reducing the rate of this reaction significantly lowers the overall corrosion rate, preserving the structural integrity and extending the lifespan of the steel rebar within concrete structures.

Mixed Protection Mechanisms: Type of Inhibitor: Can be Organic, Inorganic, Green, or a Combination.

As an example, Sodium Monofluorophosphate, primarily recognised as an inorganic inhibitor, is also an effective bipolar concrete penetrating corrosion inhibitor. It excels in deeply penetrating concrete, offering comprehensive protection against corrosion by impacting both anodic and cathodic reactions within the steel reinforcement.

Understanding Chlorine Corrosion in Concrete

Chlorine corrosion in concrete occurs when chloride ions penetrate the concrete and reach the steel reinforcement, commonly from seawater. These ions disrupt the steel’s protective oxide layer, accelerating corrosion. It’s effectively managed by anodic or mixed corrosion inhibiting admixtures, such as calcium nitrate (anodic, inorganic).

Understanding Carbonisation in Concrete

Carbonisation in concrete happens when carbon dioxide from the environment reacts with calcium hydroxide in the concrete. This reaction reduces the pH of the concrete, weakening its protective properties against steel corrosion. It’s effectively managed by anodic or cathodic corrosion inhibiting admixtures, such as sodium nitrate (anodic, inorganic) or lithium nitrate (cathodic, inorganic).

Why Invest in Corrosion Inhibiting Admixtures?

Investing in corrosion inhibiting admixtures is crucial for extending the lifespan and maintaining the structural integrity of concrete constructions. These admixtures effectively prevent the costly and hazardous effects of corrosion, ensuring long-term durability and safety and ultimately leading to significant cost savings in maintenance and repairs.

Strategic Corrosion Management in Construction

Managing corrosion in concrete structures involves a detailed understanding of corrosion types so you can select the appropriate preventive measures. Incorporating advanced corrosion inhibiting admixtures in construction not only maximises the lifespan of the infrastructure but also supports sustainable and safe construction practices. For expert advice on selecting suitable corrosion inhibitors for your next project, contact SPG Go Green or call our professional team today.


How do I choose the right corrosion inhibiting admixtures for my project?

Selecting the appropriate corrosion inhibiting admixtures depends on your project’s environmental conditions and specific requirements. Consulting with experts in the field is advisable to make an informed decision.

Are corrosion inhibiting admixtures safe for all types of concrete structures?

Most corrosion inhibiting admixtures are safe for concrete structures, but it’s essential to consider the specific environmental impact and structural needs before making your final decision.

Can existing structures be treated with corrosion inhibitor concrete admixtures?

Yes, existing structures can be treated with certain types of corrosion inhibitor concrete admixtures, especially those designed for penetrating existing concrete to reach the steel reinforcement.