Development of electrochemical impedance method for rating the efficiency of concrete reinforcement inhibitors

Cilj ovog rada bio je razviti novu metodu za ocjenjivanje efikasnosti inhibitora korozije koji se dodaju u smjesu betona prilikom miješanja i djeluju na površinu integriranog metala. Pripremani uzorci koriste puno manje materijala od konvencionalnih metoda, pregledniji su, te omogućuju kasniji detaljni pregled metala i utjecaj betona i inhibitora na njegovu površinu. Ispitivana su tri komercijalna inhibitora dokazane učinkovitosti u odnosu na kontrolu, odnosno beton bez dodataka i kontrolu sa dodatkom klorida. Korišteni su Q paneli od ugljičnog čelika i stakleni cilindri koji su tvorili radnu ćeliju. Unutar cilindara su ulijevane različite kompozicije betona sa i bez inhibitora, te nakon sušenja zasićeni kalcij hidroksid s dodatkom klorida koji je služio kao elektrolit. Pripremano je po tri uzorka istog sastava kako bi se isti mogli usporediti, te ukloniti pogrešku prouzrokovanu lošijom pripremom. Mjerenja su izvršena koristeći elektrokemijsku impedancijsku spektroskopiju, očitavanjem korozijskog potencijala, te provedbom mjerenja kontaktnog kuta i slobodne energije površine. Rezultati rada pokazuju najbolju inhibiciju korozije u sustavu s inhibitorom C (djelotvornost 87,4 %), nešto lošije rezultate pokazuje sustav s inhibitorom B (djelotvornost 63,2 %), dok najlošije rezultate, vrlo slične kontroli s dodatkom klorida ima sustav s dodatkom inhibitora A(djelotvornost -15,2 %). Dobiveni rezultati dokazuju efikasnost korištenih inhibitora i njihove razlike, te potvrđuju djelotvornost razvijene metode.The purpose of this paper was to develop a new method for evaluating the efficiency of corrosion inhibitors that are added to the concrete mix during mixing and act on the surface of the integrated metal. Prepared samples utilize much less material than conventional methods, they are easy to observe, and afterwards they allow a more detailed overview of the metal and the impact of the concrete and inhibitors on its surface.Three commercial inhibitors with proven efficiency were tested, along with control without any additives and control with the addition of chlorides. Carbon steel Q panels and glass cylinders were used for the working cell. Different concrete compositions with and without inhibitors were molded inside the cylinders. When setting was finished, saturated calcium hydroxide with the addition of chlorides was poured inside cylinders, which served as an electrolyte. Three samples of the same composition were prepared to compare and eliminate the mistake caused by poor preparation. The measurements were performed using electrochemical impedance spectroscopy, corrosion potential reading, and contact angle and free surface energy measurements. The results show the best inhibition of the corrosion in system with inhibitor C (87.4 % efficiency), the system with inhibitor B showed slightly worse results (63.2 % efficiency), while the least effective, and very similar to the control with the addition of the chlorides, was a system with the addition of inhibitor A (-15.2 % efficiency). The obtained results demonstrate the efficiency of the used inhibitors and differences between them and confirm the effectiveness of the developed method