Study of corrosion protection of steel rebars in concrete by sacrifical anodes of Zn-AI-ln alloys and by green inhibitor locust bean gum

摘要

Reinforced concrete such as any other material is subject to the spontaneous destruction processes respectively corrosion, which in most cases is caused by corrosion of reinforcement in concrete. Corrosion of steel in concrete can be caused by: carbonation, the presence of ions such as chloride, sulfate or other aggressive substances, which are usually present in various industrial facilities. The Corrosion of steel reinforcement in concrete is of great concern in the view of safety and durability of reinforced concrete structures. Corrosion undermines the physical integrity of structures and can lead to destruction of property and loss of life. The objective of this study was to investigate the behavior of sacrificial anodes from alloy Al-Zn-ln and green inhibitors as adittives in mud concrete, in separate exsperiments. In the first study, the experiments are performed in solutions (SPS) that simulate composition of liquids in pore of concrete, chloride ion content was 3.5%, while the pH is adjusted by the addition of H_2SO_4. Anodes of Al-Zn-ln alloys are used in cathodic protection (CP) systems as sacrificial anodes. Galvanic anodes Al-Zn-ln were prepared from alloys with different contents of In (0.17 and 0.25%). Obtained results during anodic polarization of these Al- Zn-ln anodes in SPS solutions show that these anodes are not passivated in environments where the pH was 8 and have similar behavior betwen them.. In these CP models anode / cathode surface ratios have two different values: 1:60 and 1:120, while the pH of the solutions was 14 and 8. From the measured values of electrochemical parameters in CP models with Al-Zn-ln alloy anodes were shown that steel rebars in concrete can successfully protected from corrosion. The aim of the second study was to investigate the efficiency of green inhibitor added in concrete. The concrete samples were exposed in aggressive media H_2SO_4 1M and 10~(-3) CI~-. As corrosion inhibitor was used locust bean gum, a green inhibitor (1g/l). Half-cell potencial, polarization resistance and Tafel extrapolation methods are used for inhibitor efficiency testing. The results shows high resistance polarization and low corrosion rate for concrete sample with green inhibitor. The corrosion rate decrease approximately 83% in presence of locust bean gum.