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Surface applied corrosion inhibitors (SACI) are widely used to mitigate corrosion process of steel reinforcement in concrete. But they remain controversial as to their effectiveness and the ability to compare materials from different manufacturers
and technologies. They are applied onto the surface of
hardened concrete and penetrate towards steel reinforcement. This paper discusses the corrosion inhibition performances of
dual-phase surface applied corrosion inhibitor and the efficiency of the corrosion inhibitor is assessed by selected testing procedures in BAM laboratories.
Due to the corrosion resistance of carbon steel, bridge constructions are currently protected against corrosion by applied coating systems. These coating systems need to be renewed after approximately 25 50 years. Galvanized constructions without any welding areas at the construction site could be prepared as grouted joints and can be used without any renewing for about 100 years.
Exposure sites and outdoor exposure have always been a part of atmospheric corrosion research providing the “final answer”, although at the cost of long exposure times. Individual exposure programs such as ISOCORRAG, MICAT and ICP Materials have resulted in collaborative networks of exposure sites. So far, however, there has been no collective effort to put together currently active sites in a comprehensive manner and across programs and nations. The information collected in the catalogue is possible thanks to the work of all individual site managers listed as contact persons, efforts of members of Working Party 25 (WP25) Atmospheric Corrosion of the European Federation of Corrosion (EFC) and financial support of the EFC. With this Catalogue you can both get a general overview of what is available and be guided if you are looking for a particular environment with certain characteristics.
The presentation shows systematic investigations to describe the corrosion and corrosion product formation processes of pure zinc under the climatic conditions currently prevailing in the Federal Republic of Germany. The investigations in their entirety aim at questioning current and establishing new ways of looking at the formation of corrosion products of pure zinc under atmospheric corrosion conditions. Thus, they make a significant contribution in understanding corrosion protection by zinc and zinc coatings. In particular, the focus is placed on the initial stage of the corrosion product formation. A systematic investigation of this time range, which is characterized by very reactive corrosion products, is only made possible by using gel-type electrolytes. The short periods of time at the beginning of weathering is now measurable and their influence on the formation of corrosion products and the kinetics of layer formation describable. By combining the new electrochemical approach with gravimetric, microscopic and analytical methods, new insights could be gained both on a methodic and scientific level.
Galvanic corrosion protection by embedded zinc anodes is an accepted technique for the corrosion protection of reinforcing steel in concrete. Galvanic currents flow between the zinc anode and the steel reinforcement due to the potential difference that is in the range of a few hundred mV.
The ion distribution was studied on two steel reinforced concrete specimens admixed with 3 wt.% chloride/wt. cement and galvanically protected by a surface applied EZ-anode. On both specimens, a zinc anode was embedded and glued to the concrete surface by a geo-polymer-based chloride-free binder. At one specimen, the EZ-anode was operated for 2,5 years, the EZ-anode at the other specimen was not electrically connected to the reinforcement, this specimen serves as a reference. Both specimens have been stored under identical conditions. The ion distribution between the anode (EZ-ANODE) and cathode (steel reinforcement) was studied by laser-induced breakdown spectroscopy (LIBS) after 7 months, 12 months, and 2,5 years. Results of the LIBS studies on the specimen with activated EZ-anode after 7 months, 12 months, and 2,5 years and of the reference specimen after 2,5 years are reported. Results show that diffusion of ions contributes to the changes in the ion distribution but migration, especially of chlorides towards the EZ-anode is significant despite the weak electric field – several hundred millivolts - generated by the galvanic current. Results show that chloride ions accumulate near the zinc-anode as in water-insoluble zinc-hydroxy chlorides - Simonkollite.
The screening of coatings shows that the modification by adding individual pigment was not sufficient to protect carbon steel even during a short-term exposure, indicated by the discoloration after only seven days of exposure.
Electrochemical tests indicated that the coating cathodically protects carbon steel or slows down the corrosion reaction.
A long-term exposure test confirmed that the PANI/SiO2 modified coating successfully protects the carbon steel in the Sibayak artificial geothermal water at 150 °C for 6 months.
Corrosive geothermal brines are a major challenge to geothermal power-plants. For cost reasons, plant designers favorize low alloyed steels, e.g., carbon steel, which are susceptible to uniform and localized corrosion when exposed to geothermal brines having acidic and saline properties. To solve such problem, coatings or inhibitors would be a protective solution as an alternative to the use of high alloyed materials.
This study investigated a coating system consisting of polyaniline/silicon dioxide basing on locally available resources. Protection against corrosion of carbon steel is shown by long-term exposure and electrochemical tests of coated carbon steels, performed in an artificial acidic and saline geothermal brine, comparable to real conditions at a site in Indonesia.
Therefore, an integrated coating system is presented for corrosion protection, combining the electro-chemical functionality of polyaniline and the physical advantages of silica.
Evaluation of corrosion resistance of metallic materials is essential to assure safe and reliable operation of geothermal sites. One need to be aware that corrosion is not a material's but a system property, determined by medium, material and construction aspects. Various corrosion types have to be evaluated. Conditions in laboratory shall reflect on-site reality. Depending on brine composition and temperature suitability of metallic materials can be ranked. Most important outcome of the research is that highly saline geothermal brines require high alloyed materials, for safe long-term operation.
Integrated Coating System for Corrosion Protection of Carbon Steel in Artificial Geothermal Brine
(2022)
Corrosive geothermal brines are a major challenge to geothermal power-plants. For cost reasons, plant designers prefer to use carbon and low alloyed steels, which are susceptible to uniform and localized corrosion when exposed to geothermal brines having acidic and saline properties. To solve such problem, coatings or inhibitors would be a protective solution as an alternative to the use of high alloyed materials.
This study investigated a coating system consisting of polyaniline/silicon dioxide based on resources locally available in Indonesia. Protection against corrosion of carbon steel was shown by long-term (28 day) exposure and electrochemical tests of coated carbon steels, performed in an artificial acidic and saline geothermal brine, comparable to the conditions encountered at a site in Indonesia.
Therefore, an integrated coating system is proposed for corrosion protection, combining the electrochemical functionality of polyaniline and the physical advantages of silica.