The use of calcium nitrite as a corrosion inhibiting admixture in the concrete mix is well established. However, trials of inhibitor treatments to hardened concrete after corrosion damage has been observed are comparatively recent. Although new materials are being produced and tested, the range of inhibitors presently available can be summarised as follows:

• Several proprietary formulations of vapour phase inhibitors, based on volatile amino alcohols which create a molecular layer on the steel to stop corrosion
• Calcium nitrite, an anodic inhibitor in a mixture to aid penetration into concrete
• Monofluorophosphate which seems to create a very alkaline environment as it hydrolyses in the concrete.

In principle, corrosion inhibitors are applicable in any situation. However, for the present understanding of the materials available and the limited field testing the following applications for inhibitors can be considered:

• carbonation or low to modest chloride levels (less than 1% chloride by weight of cement)
• low cover (less than 20mm)
• penetrable concrete (carbonated or corrosion damaged in less than 20 years)
• barrier coating applied after application
• corrosion monitoring installed in concrete to assess effectiveness with time
• apply before high corrosion rates are established

Application of an inhibitor to any element with an accessible surface is simple and inexpensive. Limited results of field trials are available.

What we can do for you

• Review the condition of your structure
• Recommend repair options
• Provide designs and performance specifications
• Provide lists of qualified and experienced contractors
• Provide corrosion monitoring after treatment