As usual, the 3-country corrosion conference in Dübendorf (Switzerland) on March 31 and April 1 looked to the future. This time, however, the focus was not on hydrogen as in the past two years, but on corrosion issues in the city of the future. Topics included corrosion on bridges, corrosion problems with metal fastenings in timber construction, new types of melts as heat transfer media in solar power plants and corrosion risks in urban areas.
The conference takes place alternately in Germany, Austria and Switzerland each year. Corrosion topics may not always have to do with coatings, but corrosive mechanisms are always phenomena that provide insights for electroplating and other coating technologies. The event is therefore a must for the Galvanotechnik editorial team.
The conference takes place in alternating years in Germany, Austria and Switzerland.
Last year, Vienna was the venue for the expert meeting, before that Frankfurt am Main. This year, the highly specialized community of experts met in Dübendorf near Zurich on the premises of the Swiss Federal Laboratories for Materials Science and Technology (Empa). The conference was organized by Empa, the Swiss Society for Surface Engineering (SGO), the Swiss Society for Corrosion Protection (SGK), the Society for Corrosion Protection (GfKORR) from Germany and the Austrian Society for Metallurgy and Materials from Austria.
Urban infrastructure buildings
The first speaker was Matthias Sulzer, Head of Empa's Department of Engineering Sciences. His topic: "Innovations in construction and energy in the city of the future". Sulzer emphasized that the greenhouse gas emissions of modern cities could be reduced to net zero by 2050 and theCO2 concentration in the atmosphere could be stabilized at 450 ppm. His research institute is therefore working on special concrete and asphalt. In addition, in order to reduce the high greenhouse gas emissions from concrete, he discussed the storage of carbon, which could be used to produce black carbon by means of methane pyrolysis - a raw material for Switzerland, which is poor in raw materials. At the same time, this black carbon granulate, which is virtually recycled, could be incorporated into concrete, thus making itCO2-free.
The second speaker was Gino Ebell from the Federal Institute for Materials Research and Testing (BAM), who spoke about the Carola Bridge that collapsed in Dresden last September. Galvanotechnik published the topic in a two-part article in issues 5 and 6. Ebell cited brittle broken prestressing wires as the cause of the collapse. However, such a break is inconceivable without hydrogen embrittlement, which raises the question of the origin of the hydrogen. Ebell presented magnetic stray field measurements carried out by BAM, which revealed a high level of moisture in the structure. When the bridge was built in 1969, the level of sulphur dioxide in Dresden was also extremely high at 1050 µg per cubic meter. The GDR had a considerable SO2 environmental problem, which was caused by the intensive use of brown coal in power stations and industrial plants. If the environmental conditions during construction are taken into account, the result is a pH value of 3.55, i.e. a very acidic environment.
His conclusion: The hydrogen loading of the prestressing steel was caused by rainwater and acidic sulphur during construction. This led to hydrogen embrittlement, which resulted in the gradual failure of the prestressing steel. Significant fractures were also possible without visible cracks, so the imminent collapse of the bridge was not readily apparent. Ebell warned that 75 bridges in Berlin alone were at risk due to similar problems.
Florian Vogel from the Department of Environment, Civil Engineering and Geomatics at ETH Zurich took a similar line to Ebell with his topic "Crevice corrosion on riveted steel bridges". He 
Alexander Tomandl from Hilti spoke about timber construction and which corrosion protection is suitable for the metallic construction elementspresented the project of a repaired bridge in the canton of Thurgau, which was already showing rust again a few years after the repair. The cause was not just crevice corrosion, but a mixture of galvanic corrosion and corrosion of the hydrogen type, according to Vogel's analysis. In order to adequately protect the bridge, it was completely dismantled and later riveted back together, he reported. The metal of the bridge was then treated with spray galvanizing, primer, micaceous iron oxide and top coat.
Alexander Tomandl from Hilti in Liechtenstein stepped up to the lectern next. His topic: Innovative fastening techniques in timber construction and challenges for corrosion protection. He began by addressing the question of what timber construction can achieve in the city of the future, referring to an 18-storey timber building in Vienna. "Timber construction is on the increase", he observed, and 18%CO2 could be saved in the process. The generally assumed fire risk of the special wood used in timber construction is also low, as it chars on the outside but remains intact on the inside. Metal elements of these houses are not exposed to the weather as they are completely enclosed by wood. Nevertheless, there is a long-term risk of corrosion: in oak wood, for example, galvanized zinc coatings can easily rust, as can zinc lamella coatings. In order to guarantee corrosion protection for 50 years, very thick zinc coatings would be required, which is not feasible.
The last speaker of the first day was Jörg Vogelsang from Sika Technology AG. He dealt with the question of what influence scratch markings on coated substrates have on corrosion protection. He justified his choice of topic by saying that this topic is always a source of discussion. He presented various investigations using different scribing tools, including cases where deep cuts had been made through the coating into the substrate. However, Vogelsang was unable to make any conclusive recommendations, as there is a lack of comparability in scoring, as the different types of scoring are not standardized. The passionate amateur chef, who was about to retire at the time of the conference, was presented with a molecular chef training course as a farewell gift.
The participants were then able to visit the so-called Nest, a research and innovation building at Empa where new technologies, materials and systems are tested, researched and further developed under real conditions. The Nest offers a fascinating mix of different construction methods, including a 3D-printed spiral staircase. The modularly constructed apartments are, among other things, energy-optimized and make use of natural cooling in summer and natural heating in winter.
Empa's so-called Nest shows differently constructed and designed modular housing units. The energy- and resource-efficient living of the future is being researched here
Energy storage and conversion
The energy storage and conversion topic block started the next day with the first speaker Ceyhun Oskay from the Dechema Research Institute in Frankfurt am Main. The moderator was SGO head and Empa group leader Patrik Schmutz. Oskay spoke about further developments in solar tower technologies and made reference to the large solar power plant in Ouarzazate in Morocco. It is the second largest solar power plant in the world and cost nine billion US dollars. A technically similar pilot plant is also located in Jülich. However, the plant in Morocco recently broke down due to a failure of the molten salt used. Oskay then turned his attention to the question of how solar power plants like this could become competitive, possibly also with other smelters. One possibility is nitrate melts as a heat storage medium, in which metals are also used as heat transfer media, such as chromium, nickel or iron. After weighing up the advantages and disadvantages in terms of corrosion, Oskay presented copper chromite as a suitable medium.
Host and SGO CEO Patrik Schmutz (right) bid farewell to Jörg Vogelsang on his retirement with a voucher for training as a molecular chef
Prof. Gregor Mori from the University of Leoben also demonstrated his talent for communicating technical content in an entertaining and understandable way during his lecture in Dübendorf
The moderator of the first day, Gregor Mori, gave a lecture on the topic of "Hydrogen storage in high-strength steel containers made of clad plates". The topic is based on the obvious prospect that, in view of the energy transition and the switch to renewable energies, natural gas storage facilities will have to be converted into hydrogen storage facilities.
At the end of the second thematic block,Lars Jeurgens from Empa discussed the question of the interactions between atomic hydrogen and passivating oxide layers. Ultimately, a self-healing oxide film is best, for example when it comes to pipelines or similar lines. Stainless steel on which a protective passive layer of chromium oxide forms would also be conceivable. X-ray photoelectron spectroscopy (XPS) can be used to observe what happens at the interfaces. However, XPS systems are rare; there is only one in Switzerland. The researchers are currently investigating how atomic hydrogen interacts with passivating surfaces under laboratory conditions in a glove box with an argon atmosphere. The argon atmosphere is important because the oxides in the air change immediately, explained Jeurgens.
Sustainable construction methods in an urban environment
Max Kloger, Tiroler Rohre, and Anika Stelzl from Graz University of Technology know how pipes are protected against corrosionThetwo speakers Max Kloger, Tiroler Rohre, and Anika Stelzl, Graz University of Technology, spoke about models for predicting the condition of different generations of ductile iron pipes. These are usually protected with different coatings, either with tar only, with a layer system of zinc and bitumen or with zinc only. When pipes are installed in the ground, the soil conditions play a role in corrosion damage - clayey soils are not good, for example - as does the coating. Tar provides protection for around 50 years, bitumen for around 80 years and zinc for more than 80 years.
Dennis Joos from the Swiss Society for Corrosion Protection (SGK) then addressed the topic of "Corrosion problems in urban areas". He made it clear that even in the densely built-up area of a city, current flows constantly promote corrosive processes. He illustrated this with an example. Water pipes in the ground can act as an anode with railroad tracks above them as a cathode, leading to stray currents and corrosive processes. To prevent this, cities would have to equip the water pipes with insulating flanges or use insulating protective pipes or cathodic corrosion protection with external anodes.
The conference was concluded by Rebecca Achenbach from RWTH Aachen University. She spoke about future binder types and their influence on the corrosion protection of reinforcement in reinforced concrete. She presented some building materials and binders as well as their influence on the reinforcement and warned that the passivity of the reinforcement cannot be assumed for every new type of binder, even if the pH value suggests it.
All photos: Robert Piterek
