Accelerated evaluation of corrosion inhibition by means of the integral corrosion test

Abstract

Corrosion inhibitors, either added in the concrete mix or applied in corroding structures, are used to avoid or decrease reinforcement corrosion. Their efficiency is usually noticed by measuring the corrosion rate in several exposure conditions to detect the possible decrease of the corrosion rate or a repassivation. In present paper is presented the use of the named “integral corrosion test” to evaluate the inhibitor efficiency. This test consists in a migration test in which the cubic specimen has a bar embedded in its centre which starts to corrode when the chloride front arrives to it. It is called “integral” because it enables the consecutive detection of the diffusion coefficient, the chloride threshold and the corrosion rate. The diffusion coefficient is measured from the time taken until the steel bar starts to corrode, the chloride threshold by analysing a small sample of the steel/concrete interface just after depassivation and the corrosion rate, by measuring it in a twin specimen after the disconnection of the external voltage. The results indicate that the presence of inhibitors delay the depassivation time and decrease the corrosion rate developed while the chloride threshold appears to be higher. Then the test seems a good accelerated mode of studying inhibitor efficiency and can be also used to classify concrete resistance to chlorides.