Field Tests and Experience with Corrosion Inhibitors

Field Tests and Experience with Corrosion Inhibitors 

Only calcium nitrite, introduced more than thirty years ago, has a long and proven track record as a corrosion inhibitor for reinforced concrete [1,4]. MFP and alkano-lamine-based organic inhibitor blends are increasingly used but unfortunately most of the commercial apphcations lack rigorous control of the inhibitor effect. One of the very few comparative field tests on chloride-contaminated concrete studied MFP and a proprietary alkanolamine inhibitor added in the side-walls of a tunnel (16). The inhibitors were applied by the producers. The measurements of macrocell currents and half-cell potential mapping revealed that both inhibitors were virtually ineffective at the chloride concentrations of 1-2 % by mass of cement present [16]. 

Other field tests with proprietary vapour-phase inhibitors [17] in a parking garage with chloride-contaminated precast slabs did not show encouraging results. Corrosion-rate measurements showed a reduction of 60% in areas with initially intense corrosion but also an increase of corrosion rate in areas with low corrosion rates. On structures from 1960 with an admixed-chloride content higher than 1% by mass of cement, already featuring patch repairs, a three-year corrosion rate survey showed lower corrosion rates in the treated areas compared to untreated ones, but cracking and spalling increased also in the treated areas [18]. 

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