Galvanised Rebar

Reinforced concrete is an important building material used in a wide variety of structures, such as highway bridges, parking lots, homes, office buildings and ditches. In most cases, the steel bars in reinforced concrete do not require additional external corrosion protection to prevent corrosion. This is because the highly alkaline environment of concrete forms a thin oxide layer on the surface of the steel bars, which protects the steel from further corrosion, a so-called "passivation" effect.

However, in some cases, this passivation effect may not be effective enough or even fail completely. These situations may include:

The concrete has cracks, voids, pinholes or a thin protective layer. These defects may expose the steel bars directly to the external environment, increasing the risk of corrosion.

The alkaline environment of the concrete is neutralized (carbonated). Over time, the alkaline substances in the concrete may react with carbon dioxide in the air, causing the concrete to become less alkaline, thereby weakening the passivation protection for the steel bars.

Chloride ions penetrate into the concrete. In marine environments or roads where salt is spread to remove snow in winter, chloride ions may penetrate through the pores of the concrete and react with the steel bars, causing corrosion.
These situations usually occur in the outermost parts of the building. Defects in reinforced concrete have become more prevalent due to increased salt content and impurities in the atmosphere. Defects in different concrete structures are more common today than before. Once corrosion begins, it is very difficult and expensive to repair.

Therefore, protecting the steel from corrosion is becoming increasingly important in many concrete applications. This may require additional anti-corrosion measures such as using galvanized steel bars, applying anti-corrosion coatings to the steel surface, or adopting other anti-corrosion technologies to ensure the long-term durability and safety of reinforced concrete structures.

Galvanized rebar is bare steel that is covered with a protective zinc metal coating. This zinc coating acts as a barrier to corrosive elements when the rebar is embedded in concrete. In addition to the barrier protection provided by the zinc layer, it also provides a cathodic protection mechanism. Under this mechanism, when the zinc layer comes into contact with bare steel (such as the voids on the surface of the galvanized rebar), the zinc will preferentially corrode, thereby protecting the surrounding steel parts from corrosion.

When galvanized rebar is embedded in concrete, its zinc coating also exhibits other favorable anti-corrosion properties. These properties make it an effective coating material for combating corrosion. Specifically:

• Barrier protection: The zinc coating acts as a barrier that blocks moisture, oxygen, and other corrosive substances from direct contact with the rebar, thereby slowing or preventing the corrosion process.
• Cathodic protection: In galvanized rebar, the zinc has a lower electrode potential than iron, so when they are in an electrolyte (such as concrete pore fluid), the zinc will preferentially corrode as the anode, while the iron is protected as the cathode. This cathodic protection mechanism further enhances the corrosion resistance of galvanized rebar.
• Good adhesion: The galvanized coating has good adhesion to the steel bar substrate, which can ensure that the coating is not easy to fall off or peel off during long-term use.
• Durability: The galvanized coating has a long service life and can maintain its anti-corrosion performance under harsh environmental conditions.