Corrosion inhibitors for steel in concrete - an update on the ongoing discussion

10 years ago a first state of the art report “Corrosion Inhibitors for Steel in Concrete” has been published as EFC 35. Industry continued to develop and improve systems that can be applied as mixed-in inhibitors (preventative in new constructions) or as surface-applied inhibitors (curative, restoration) on concrete. Numerous research reports and papers have been published on laboratory and an increasing number of field studies that are summarized in this paper. Despite still conflicting results it can be stated that admixed inhibitors can delay the onset of corrosion significantly, once corrosion started no reduction in corrosion rate has been found. Surface applied inhibitors show positive results at chloride concentrations lower 0.5% and with beginning corrosion. At chloride contents above 1% and with corroded reinforcements a significant reduction in corrosion rate is difficult to achieve. For the end user it is difficult to get the overview on “corrosion inhibitors” because products with different trade names con-tain the same or similar active substances, the exact compositions can vary frequently and can be different from one region to the other.