The use of penetrating corrosion inhibitors as a treatment for structures corroding due to chloride ingress

摘要

Corrosion inhibitors are used for delaying the onset of corrosion in new concrete construction. Penetrating corrosion inhibitors have been developed that can be applied to the surface of an existing concrete structure and migrate to the level of the steel. These have also been applied to corroding structures in an attempt to either halt corrosion or to reduce the rate at which it is occurring. An investigation was carried out into the effectiveness of this repair technique. A commercial organic-based corrosion inhibitor was used with a variety of different concrete mixtures. A 3% NaCl solution was ponded on the surface of 17 concrete samples for each of six mixtures to start them corroding. For eight samples in each mixture, this treatment was stopped at a low level of corrosion (approximately 0.2 μA/cm~2 as measured by linear polarization), while for the remaining nine this treatment was continued to a high level of corrosion (approximately 0.8 μA/cm~2). While most of the samples exhibited surface staining from the corrosion products, the concrete was not visibly cracked. The corrosion inhibitor was then applied incrementally to the surface of the concrete while ponding of the samples with tap water continued between applications. This was carried out until the corrosion had stopped, or twice the recommended level of inhibitor had been applied. The chloride concentration and presence of inhibitor at the level of the steel was investigated at that stage. The corrosion inhibitor was effective in stopping corrosion when the chloride concentration at the level of the steel was below the enhanced threshold concentration determined from treated, previously uncontaminated specimens.