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The corrosion behavior of galvanized steels and zinc components under atmospheric exposure depends mostly on the corrosion product‐based cover layer formation under the prevailing conditions. The use of agar‐based gel electrolytes makes it possible to use electrochemical methods to obtain a characteristic value from these cover layers that describe their current and future protective capacity. It is shown here that different states of galvanized steel can be distinguished very well under laboratory conditions and that this method is also suitable for use under practical conditions. Based on the characteristic values and assuming future time of wetness, it is very easy to draw up a forecast for the future corrosion rate, which provides plausible values. [ABSTRACT FROM AUTHOR]

Corrosion monitoring of reinforced or prestressed concrete structures has become increasingly important in recent years. Areas of application include components that are no longer accessible after completion or where potential field measurements cannot be carried out due to existing coatings. Corrosion monitoring can also be used to monitor the progress of corrosion in corroding systems, e.g. to prove the success of repair measures according to repair principle 8 in accordance with EN 1504‐9 or repair method 8.3 in accordance with the DIBt repair guideline. It also could be used to prove the functionality of cathodic corrosion protection systems in accordance with ISO 12696. Despite the increasing importance of corrosion monitoring, no guidelines or recommendations existed until 2018. This gap was closed by the English version of specification B12, "Corrosion Monitoring of Reinforced and Prestressed Concrete Structures," of the German Society for Non‐Destructive Testing, which was published in 2021. This article introduces specification B12 by explaining the basic measurement principles and illustrating the potential of corrosion monitoring in new and existing buildings. [ABSTRACT FROM AUTHOR]

Alkali-activated fly ash mortars were studied with regard to durability-relevant transport coefficients and the electrochemical behaviour of embedded carbon steel bars on exposure of the mortars to leaching, carbonation and chloride penetration environments. The transport coefficients differed considerably between different formulations, being lowest for a mortar with BFS addition, but still acceptable for one of the purely fly ash-based mortars. Leaching over a period of ~300 days in de-ionized water did not lead to observable corrosion of the embedded steel, as shown by the electrochemical data and visual inspection of the steel. Exposure to 100 % CO2 atmosphere caused steel depassivation within approx. two weeks; in addition, indications of a deterioration of the mortar were observed. The results are discussed in the context of the different reaction products expected in highand low-Ca alkali-activated binders, and the alterations caused by leaching and carbonation.

The critical chloride content Ccrit is an indicator of the corrosion resistance of reinforcing steels in concrete. In this article, several experimental methods for determining the critical chloride content Ccrit of mild and alloyed (12% Cr) steel in cementitious materials are compared. The methods used include accelerated polarization tests and tests employing more natural (unpolarized) conditions in which chloride ingress occurs by diffusion and capillary uptake. The advantages and disadvantages of the methods are discussed, in particular, against the objective of reaching a compromise between applicability to practice and feasibility in laboratory testing. [ABSTRACT FROM AUTHOR]

Literature data on the influence of concrete cracks on corrosion propagation of reinforcing steel are contradictory. This might be due to very different exposure and test conditions but also to a lack of time-resolved data in cyclic wetting–drying exposure. Here, the influence of the environmental conditions on the corrosion rates in cracked concrete is studied experimentally. The results show that the corrosion rate in cracked concrete depends on the duration of wetting and drying phases and the relative humidity (RH) during the drying phase. The lower the ambient RH in the drying phase, the faster the cracks dry, which depresses the corrosion rate in the periods between the wetting events. A model is proposed to estimate corrosion rates in cracked concrete cyclic wetting/drying exposure. [ABSTRACT FROM AUTHOR]

Determination of the corrosion‐inducing chloride content of stainless ferritic reinforcing steels in mortar The corrosion protection mechanism for stainless steel in concrete is different than for unalloyed steel. In carbonated concrete, stainless steels are in a passive state and do not have any uniform corrosion. The chloride content for the initiation of pitting corrosion on stainless steels in concrete depends not only on the content of alloying elements (above all chromium) and the surface condition. It also depends on the concentration ratio between OH– and Cl– in the electrolyte. It can be expected that lower chloride contents can initiate corrosion in carbonated concretes than in concretes with higher pH values. This ap‐plies especially to stainless steel with low chromium contents such as products made of the material 1.4003 (X2CrNi12). In order to determine the critical corrosion‐inducing chloride content using the example of a pickled ferritic chromium steel available on the market, extensive laboratory tests were carried out at the Federal Institute for Materials Research and Testing (BAM). In accelerated corrosion tests in alkaline and carbonated mortars, the critical chloride contents in the phase boundary between reinforcing steel and mortar were determined and evaluated by means of laser induced breakdown spectroscopy (LIBS). [ABSTRACT FROM AUTHOR]

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