Understanding and Mitigating Anchor Rod Corrosion

Introduction

Anchor support is a widely used support method, especially in civil engineering and underground construction, which is mainly made of steel and is usually buried in underground rock and soil layers. However, due to the special characteristics of the working environment, anchor rods will inevitably be affected by corrosion, which will adversely affect the safety and durability of the project. Therefore, it is crucial to have a deep understanding of the corrosion mechanism of anchor rods and to adopt effective protection methods.

Corrosion Mechanisms of Anchor Rods

The corrosion of anchor rods in underground settings encompasses four primary mechanisms: chemical corrosion, electrochemical corrosion, high-stress corrosion, and scattered current corrosion.

Chemical Corrosion

Occurring when anchor rods are exposed to chemical substances in groundwater or soil with imbalanced acidity and alkalinity, chemical corrosion initiates a gradual weakening of the anchor's material strength.

Electrochemical Corrosion

Electrochemical corrosion is one of the most common and major anchor corrosion mechanisms. This type of corrosion involves the contact of electrolytes from groundwater and air with the metal on the surface of the anchor rod, creating a battery effect. During this process, the metal in the anchor will gradually dissolve, leading to corrosion of the material.

High-Stress Corrosion

High-stress corrosion is usually associated with small cracks or areas of stress concentration on the metal surface of the anchor when it is subjected to significant loading or vibration. These cracks or areas of stress concentration accelerate the development of corrosion and reduce the load-carrying capacity of the anchor.

Scattered Current Corrosion

Scattered current corrosion is caused by current leakage triggered by power or electrical equipment. When the electric current passes through the surface of the anchor rod underground, it may trigger corrosion of the metal surface, which poses a threat to the durability of the anchor rod.

Protective Methods for Anchor Rods

To effectively counter anchor rod corrosion, a range of protection methods are available, selected based on project lifespan and environmental conditions.

Unprotected Products

Suitable for temporary support works (life expectancy less than 2 years) or in environments where there is no corrosion. This option is suitable for situations where the life expectancy of the anchors is not required.

Hot-Dip Galvanizing Corrosion Protection Systems

Ideal for semi-permanent support works (life expectancy between 2 and 5 years), this method involves immersing anchor rods in molten zinc to form a protective zinc layer on the surface.

Epoxy-Coated Corrosion Protection System

Similar to hot-dip galvanizing, epoxy coating enhances corrosion resistance by applying a robust epoxy coating to the anchor surface, suitable for semi-permanent support works.

Double Corrosion Protection Systems

Suited for permanent support projects with a lifespan exceeding five years, this method combines hot-dip galvanizing and epoxy coatings to extend corrosion protection duration.

Multiple Corrosion-Resistant Anchor Rods

In extremely corrosive environments, such as marine environments, multiple corrosion-resistant anchors are an option. This type of anchor combines multiple corrosion protection measures, usually including multiple layers of protection such as galvanizing, epoxy coating, and cement slurry encasement. The principle is that the galvanized and epoxyed anchor rod is placed into a PE plastic casing, and then water slurry is injected into the inner wall of the casing and between the outer wall of the casing and the borehole, which is cemented to form a multi-corrosion resistant anchor rod. This method provides the highest level of corrosion protection and is suitable for the most demanding project conditions.

Conclusion

Corrosion poses a significant threat to anchor rod safety and project durability, necessitating a comprehensive understanding of corrosion mechanisms and appropriate protective measures. The selection of suitable protection methods should be informed by project lifespan, environmental conditions, and corrosion severity to ensure long-term reliability. Sinorock is a high-tech company that has been specializing in geotechnical anchoring for 15 years. We offer a wide range of anti-corrosion anchor rod solutions, including hot-dip galvanized anchor rods, double anti-corrosion anchor rods, etc., which are suitable for different types of projects to ensure high quality and long-term reliability. Whether it is for road, rail, or water projects, or for submarine and underwater tunnels, metro tunnels, and other underground constructions, Sinorock's products provide excellent corrosion protection for a successful and long-lasting project.