Corrosion Causes of Anchor Bars and Anti-corrosion Treatment Process

In geotechnical engineering, the durability of anchor bars is the main factor affecting their service life in structures and formations. The greatest threat to the service life of anchor bars comes from corrosion. Under normal circumstances, after 20 years of installation and use of the anchor bar, the project needs to be reinforced, which is labor-intensive, time-consuming, and expensive. However, the research on the anti-corrosion and durability of anchoring systems is relatively lacking, and engineering failures caused by insufficient durability of anchor bars occur from time to time. For example, the solid steel anchor bolts in the foundation of the World Trade Center in the United States were corroded and fractured in the acidic corrosion environment formed by cinders.

 

Due to the increasing number of underwater tunnels across rivers and seas and mountain tunnels in corrosive underground environments, ordinary mortar bolts have been difficult to meet the anti-corrosion requirements of supporting structures. Engineering practice shows that the corrosion of anchor bars comes from air and groundwater, and the latter has a more obvious corrosion effect on anchor bars. The corrosion of anchor bars in the formation is mainly chemical corrosion and scattered current corrosion. The corrosive medium in the lower layer acts on the outer surface of the bars through groundwater and air, causing corrosion of the mortar and the rod body, resulting in anchorage failure.

 

 

For ordinary mortar bolts, if the grouting is not full, or cracks caused by rock stratum displacement, are likely to cause and accelerate water and air to corrode the rod body. In actual engineering, the water and air erosion of ordinary anchor bolts are mainly as follows:

1. The position of the anchor bar is not centered, which makes the place where the grouting layer is thin along the axial direction of the anchor bar susceptible to corrosion;

2. During the installation process, the grouting body may be cracked due to dryness or stratum dislocation, and the accumulation of water and corrosive media in the cracks will cause the bolt body corrosion;

3. The air is not easy to discharge during grouting, and there are air pockets at the drilling position, and the steel bars exposed to the cavitation are extremely susceptible to corrosion.

 

At present, hot dip galvanizing anchor bolts, epoxy coating anchor bolt and duplex coating are most common anti-corrosion anchor bolts.

Hot dip galvanizing anchor bolts is especially suitable for various acid, alkali mist and other corrosive environment, as well as occasions with longer service life requirements and complex environments in geotechnical engineering.

Epoxy coating anchor bolt is suitable for occasions where stratum and groundwater contain sulfides and chlorides, corroded by seawater, and environments with stray currents or corrosive medium.

Duplex coating is a combination of hot dip galvanizing and epoxy coating. Firstly the product is hot-dip galvanized and then the epoxy powder is sprayed on the surface. The anchor bolt has better anti-corrosion performance an longer service life after two kinds of anti-corrosion processes. It can not only resist ordinary chemical corrosion but also work in an acidic environment and electrochemical corrosion with stray currents.

As a professional rock anchor bolts manufacturer, Sinorock specializes in providing a variety of anti-corrosion anchor bolt systems, such as hot dip galvanizing anchor bolts, epoxy coating anchor bolt and the duplex coating anchor bolt combining the above two processes.