Year-end Sale % OFF 
Abstract
An important aspect with regard to the service life of zinc based galvanic anodes and the durability of the corrosion protection of steel in concrete is the “galvanic chloride extraction”. Chloride ions move in the electric field generated by the current, flowing between the galvanic anode and the cathodic steel. Migration leads to an accumulation of anions, e.g. chloride ions, at the anode and depletion of chlorides near the steel rebar surface. The ion migration was studied on steel reinforced concrete specimens admixed with 3 wt.% chloride/wt. cement and galvanically protected by a surface applied embedded zinc anode (EZA). The zinc anode was embedded and glued to the concrete surface by a geo-polymer based chloride free binder. The EZA was operated over a period of 1 year and the ion distribution between anode (EZA) and cathode (steel reinforcement) was studied by laser induced breakdown spectroscopy (LIBS) after 5 months, 7 months and 12 months. The results show that chloride ions efficiently migrate in the direction of the zinc-anode and accumulate there. Chloride distribution in the EZA correlates with the distribution of zinc ions generated by the anodic dissolution of the zinc anode in the binder matrix. The microstructure of the binder matrix and its interface to the zinc-anode are studied by REM/EDX – preliminary results will be reported.
Highlights
Galvanic corrosion protection of steel in concrete is based on the formation of a galvanic element when a metal which is less noble than cast iron steel, in direct contact with the concrete overlay, is electrically connected to the steel rebars
The galvanic current between the embedded zinc anode (EZA) mounted on the mortar probe stored in a climatized chamber (75% rh, 20 – 25°C) and the steel reinforcement was monitored
The evaluation of elemental distribution in the concrete/binder matrix by laser induced breakdown spectroscopy (LIBS) allows the investigation and graphical representation of the changes in the ion distribution caused by the applied electric field
Summary
Galvanic corrosion protection of steel in concrete is based on the formation of a galvanic element when a metal which is less noble than cast iron steel, in direct contact with the concrete overlay, is electrically connected to the steel rebars. A galvanic zinc anode system composed of a zinc mesh embedded into a proprietary mortar that solidifies into a solid electrolyte, installed on various civil structures (bridges, marine harbour piles, parking decks, tunnel entrances) protects the steel reinforcement reliably and efficiently from corrosion for up to 11 years [6]. The solid electrolyte of the embedded zinc anode system (EZA) is based on a tecto-alumosilicate-binder (TAS) containing additives that prevent passivation of the zinc anode, assure high and durable galvanic activity of the zinc anode and high and durable adhesion towards the concrete overlay. The electric field generated by the galvanic current, is estimated to be in the range of 300 – 600 mV, estimated from the open-circuit potential between zinc-anode and steel reinforcement, and is much lower than the electric fields usually applied (about 1 Ampere /m2) for electrochemical chloride extraction [11]. Results are reported in this paper; evaluations by REM and EDX are under way and will be reported soon in CCR (Cement and Concrete Research)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
