Corrosion mechanism and protection method of rock bolt

Rock bolting support is a very common support method, and most of the support material are steel. During supporting, it will inevitably be corroded when buried in the rock layer. So, understanding its corrosion mechanism and protection method is particularly important to the projects quality.

The corrosion formation of anchor bolt mainly includes chemical corrosion, electrochemical corrosion, high-stress corrosion and scattered current corrosion, of which electrochemical corrosion and scattered current corrosion are the main ways. This is mainly caused by the contact of corrosive media in groundwater and air with anchor bolt outer surface. It is necessary to prevent the water and air in the stratum or rock cracks from contacting with rock bolt.

Commonly isolation methods including grouting wrapping, epoxy coating or (and) galvanized, casing isolation, etc. The appropriate protection method is usually chosen according to project service life and geological corrosion situation.
Non-protective products are available in temporary support works (< 2 years) or non-corrosive environments.

In semi-permanent support engineering (2-5 years), hot-dip galvanizing corrosion protection system or epoxy coating corrosion protection system can be used according to the corrosive environment.

In permanent support engineering (> 5 years) according to the corrosive environment can choose to use hot-dip galvanizing anti-corrosion system or duplex coating anti-corrosion system.

For extremely harsh marine environments, anchor bolts with multiple anti-corrosion layers can be used.

Multiple anti-corrosion anchor bolts have more than two protective measures, usually being galvanized, epoxy treated and then wrapped with cement slurry. For more demanding projects, rock bolt with galvanized and epoxy can also be put into PE plastic casing, and then inject cement slurry into the casing pipes and holes, multiple anticorrosive anchor bolts are formed after consolidation, which have better corrosion resistance.

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