U. Nürnberger’s research while affiliated with University of Stuttgart and other places

This article describes the possible corrosion conditions for fasteners in timber outdoor constructions. In the case of fasteners (e.g., timber screws), a distinction must be made between corrosion outside the timber and in contact with the timber. In case of contact with timber, the influence of timber constituents (acetic acid and timber protection agents), which are effective when the moisture content of the timber is high, must be taken into account. In the weathered area, the corrosion exposure and the corrosion of zinc coatings in contact with timber can, therefore, be higher than in pure atmospheric corrosion. In nonweathered areas, it may be reversed due to possible concentration of pollutants outside the timber and insufficient timber moisture. Recent research results are explained using timber screws as an example. Furthermore, the requirements for zinc coatings for fasteners in timber construction are presented on the basis of the current standardisation. This article describes the possible corrosion conditions for fasteners in timber outdoor constructions. Recent research results are explained and summarised using timber screws as an example. Furthermore, the requirements for zinc coatings for fasteners in timber construction are presented on the basis of the current standardisation.

In the atmosphere of a brine bath – with a high proportion of hygroscopic chloride salts – both high strength Galfan-coated wires (zinc layer about 40 microns) as well as hot-dip galvanized wires (zinc layer about 50 microns) of the open spiral ropes above the water basin showed corrosion with red rust already after 11 years of bath operation. Hygroscopic salts with low saturation moisture such as calcium and magnesium chloride, which form highly concentrated salt solutions in a swimming pool climate, attacked both coating metals equally strong.

Present work is a wide study of the evaluation of hydrogen embrittlement (HE) risk of high strength stainless steels (HSSS) using the methodology proposed for carbon prestressing steels (FIP test). The sensitivity of the FIP method is assessed by a series of test and the influence of the material parameters, such as SS chemical composition, the microstructure and the surface morphology (cold drawn defects or presence of ribs), in the HE risk is investigated.Experimental results confirmed the higher HE resistance of HSSS compared to carbon prestressing steel. The cold drawing process promotes austenite–martensite transformation on some austenitic SS which has showed higher susceptibility for HE process to occur. The presence of defects on the HSSS wire surface, such as ribs, also contributes to reduce the resistance of these austenitic HSSS to hydrogen embrittlement. However, duplex HSSS have not shown sensitivity to HE in FIP test.

The corrosion protection behavior of hot-dip galvanized reinforcing steel justifies reduction of the minimum concrete cover required in accordance with EN 1992-1-1 and DIN 1045-1 for specific applications. The zinc coating in galvanized steel embedded in concrete is durable for all practical purposes. In situations such as those prevailing in exposure classes XC1 to XC4 (corrosion caused by carbonation), galvanized reinforcing steels are highly resistant to corrosion. Galvanized reinforcing steels are more durable than non-galvanized steels, even in chloride-containing concrete, since chloride ions are chemically bonded in the form of alkaline zinc chlorides that are not readily soluble.

The contribution is dedicated to the durability of geotechnical stabilization applications. The long-term corrosion behavior of unprotected and galvanized thread-bars for micro-piles and nails in different soils is described. The bars in the ground are embedded in an up to 20 mm thick cement mortar, which may be cracked and locally destructed. First, the corrosion-affecting parameters of the steel corrosion in the ground are described and soil classes are defined. Furthermore, an estimation of the long-term (up to 50 years) corrosion behavior was assessed on the base of information from the literature. Here the corrosion of the thread-bar in direct contact with the soil was in the center of interest. The corrosion protection of the cement mortar cover was not taken into consideration, in order to be on the safe side. On the other hand, a macrocell-corrosion of the thread-bars cannot be completely excluded, if the cement mortar casing exhibits defects and constructional and environmental corrosive conditions in the ground are fulfilled. Two cases are discussed: • element formation between sections along the thread-bar, • element formation between the thread-bar and other reinforced concrete parts.

In der DIN EN ISO 12944, Teil 2, wird die Korrosionsbelastung in Hallenbädern einer Korrosivitätskategorie C4 (starke Korrosionsbelastung) zugeordnet. Folgt man den Angaben dieser Norm, dann sollte bei verzinkten Bauteilen der jährliche Zinkabtrag in einer Hallenschwimmbadatmosphäre mehrere Mikrometer betragen. Ein solches Korrosionsverhalten stimmt jedoch nicht mit den baupraktischen Erfahrungen überein. Im vorliegenden Beitrag wird die Badatmosphäre aus korrosionschemischer Sicht betrachtet. Weiterhin werden Untersuchungen an verzinkten Bauteilen in bis zu 40 Jahre alten Hallenschwimmbädern dargestellt, und es werden Ergebnisse zur langzeitigen Zinkkorrosion in einem im Hinblick auf die Korrosionsbeanspruchung eher kritischen Bad dargelegt. Danach ist die Zinkkorrosion in den mit Leitungswasser betriebenen normalen Hallenschwimmbädern erheblich geringer als in der DIN EN ISO 12944 ausgewiesen. Es wird ein Vorschlag unterbreitet, diesem Sachverhalt im Regelwerk Rechnung zu tragen. Are reservations against the usage of galvanized building elements for indoor pools justified? According to DIN EN ISO 12944, part 2, the corrosion exposure in indoor pools falls under corrosion category C4 (severe corrosion exposure). Consequently, the zinc corrosion of the galvanized building elements exposed to an indoor pool atmosphere would amount to several micrometers. However, this kind of corrosion behaviour does not correspond with the practical building experiences. This paper pertains to chemical corrosion in a pool atmosphere. Furthermore, the investigations of galvanized building elements in up to 40-year-old indoor swimming pools are summarized and the results of long-time zinc corrosion in a rather critical pool atmosphere are presented. Accordingly, the zinc corrosion in a normal indoor pool using tap water is substantially lower than stated in DIN EN ISO 12944. It is proposed that account should be taken pertaining to this issue.

In diesem Beitrag werden Betrachtungen zur Korrosion von Anschweißankern aus nichtrostendem Stahl der Werkstoff-Nr. 1.4571 bei Naturwerksteinfassaden angestellt. Weiterhin werden Ergebnisse korrosionstechnischer Untersuchungen an derartigen Ankern aus bestehenden, bis zu 23 Jahre alten Bauwerken wiedergegeben. Bei sachgerechter Interpretation der dargestellten Zusammenhänge kann gefolgert werden, dass die im Regelwerk geforderten Maßnahmen zur grundsätzlichen Entfernung von Anlauffarben und zum Verschließen von Spalten bei atmosphärisch beanspruchten geschweißten Verbindungen im Fall der hinterlüfteten Außenwandbekleidungen aus Sicht der Korrosion technisch nicht begründet und unnötig sind. Corrosion behaviour of stainless steel weld-on anchors of claddings for external walls ventilated at the rear and made of natural stone. In the contribution considerations are made about the corrosion of stainless steel weld-on anchors of the material No. 1.4571 of claddings for external walls ventilated at the rear. Furthermore, results of corrosiontechnical investigations on such anchors of buildings which are up to 23 years old are reported. With proper interpretation of the shown connections it must necessarily be concluded that the measures in the set of rules concerning the removal of temper colours and the closing of crevices of atmospherically exposed weld-on anchors are technically not founded and unnecessary from the corrosion point of view if ventilated facades are taken into consideration.

Experience with prestressed concrete over about half a century has indicated that the corrosion resistance of conventional prestressing steel does not always satisfy, especially the prestressing steels are susceptible to chloride attack (de-icing salts) and hydrogen (hydrogen-induced stress corrosion cracking). On the other hand corrosion agents, such as chloride, condensation water, can penetrate in the concrete and arrive at the surface of steels. Hence, corrosion damage of prestressing steels can happen and, in the extreme cases, the prestressed concrete structure collapsed resulting from the failure of the tendon. In this paper, consideration is made to use high-strength stainless steels as prestressing tendon with bond in concrete. The high-strength stainless steels of qualities 1.4301 (X5CrNi18-10), 1.4401 (X5CrNiMo17-12-2), 1.4436 (X3CrNiMo17-13-3) and 1.4439 (X3CrNiMoN17-13-5) with sequence of increasing austenite stability were investigated. For application in prestressing tendon with bond in concrete the cold-drawn high-strength stainless steel of quality 1.4401 is an optimal proposition regarding its satisfactory resistance against pitting corrosion and stress corrosion cracking (SCC) in structure-related corrosive conditions. The lower alloyed steel 1.4301 has an insufficient resistance against the chloride-induced corrosion because of the lack of molybdenum and the content of deformation martensite due to the strong cold-drawing of its unstable austenitic structure.

Möglichkeiten des KorrosionsschutzesKorrosion von Stahl in BetonMaßnahmen für den zusätzlichen Korrosionsschutz von Stahl in Beton [1–3, 20, 117, 118]Besondere Korrosionsprobleme im Spannbetonbau [3, 201–203]

Serious damages in post- and pretensioned prestressed components have occurred due to hydrogen-induced stress corrosion cracking of prestressing steel. The failures happened due to onsite conditions and were favoured by the sensitivity of the steels towards hydrogen. The contribution describes the mechanism of the fracturing process, the corrosion testing of prestressing steel and gives an overview about the knowledge concerning prevention methods for application in contact with mortar and concrete.