To protect anchor bolts against environmental exposure, two principal approaches are available:
- carbon steel protected by a corrosion-resistance coating as sacrificial layer,
- corrosion resistant steel such as stainless steel with corrosion protection secured by chemical composition of steel material itself.
The appropriate solution should be selected based on the environmental corrosivity, required service life, accessibility for maintenance, life-cycle costs, and project-specific technical requirements.
Peikko DuraZinc Coating and stainless anchor bolts
Peikko offers two practical solutions for applications where anchor bolts require enhanced corrosion resistance.
DuraZinc is a surface coating method designed to protect anchor bolt threads, with a maximum coating length of 500 mm. The process is based on thermal zinc spraying, in which zinc is heated to a molten state and projected onto the steel surface using a gas stream, forming a protective sacrificial coating.
A stainless anchor bolt is manufactured by combining stainless COPRA® coupler with an anchoring part made of B500B reinforcement steel and then connected with a stainless threaded bar. To ensure that anchor bar from carbon reinforcing steel won’t be exposed to environmental conditions, the connecting coupler is produced with separated internal sockets for the exposed threaded portion and the embedded anchoring part.
DuraZinc: Experimentally validated performance
The durability of stainless steel is well established and covered by EN 1993-1-4. In contrast, the corrosion rate of the protective zinc coating is provided only for the first year of exposure and expressed as a range between minimum and maximum values, without explicit guidance on the appropriate value for design. Applying the maximum corrosion rate in all cases may lead to overly conservative service-life predictions. Therefore, experimental investigation of the actual corrosion progression is justified.
To evaluate the long-term performance of DuraZinc, a series of coated anchor bolts was exposed to a salt-mist environment representing atmospheric exposure conditions corresponding to corrosivity category C3. The total duration of the test simulated a service life of 60 years.
Following exposure, the specimens were subjected to microstructural examination to assess the progression of corrosion. The results showed that corrosion remained the underlying base steel material was unaffected by corrosion. Consequently, the structural performance of the anchor bolts remained uncompromised.
Product selection
A new white paper provides guidance for selecting between Peikko DuraZinc and stainless anchor bolts based on the corrosivity category and target service life.
DuraZinc offers a cost-effective solution for applications exposed to atmospheric conditions up to corrosivity category C3 with a design service life of 60 years. Stainless anchor bolts excel even for more demanding corrosivity conditions, longer service-life requirements, or projects where aesthetic appearance and surface finish are of particular importance.
View White Paper: Corrosion Resistance of Anchor Bolts
