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Corrosion

Corrosion plays an important role in daily life, as it often leads to premature failure of components. Investigations of corrosion at a laboratory scale should contribute to the understanding of physical, chemical and electrochemical influences. The advantage of such experiments is, in short time measurings (time-lapse), to reflect the reality well enough. One focus of this working group is the investigation of the corrosion properties of composites. On the one hand the composite aluminum-CFRP on the other the composite steel-CFRP is in the foreground. In particular, the contact area of the two materials is of interest, since the probability of failure is clearly raised. The reality is depicted in so-called swap experiments. In this case, the sample to be examined is placed in a corrosive medium for a long period. Such experiments may take several months to be completed. That period can be shortened by accelerating the corrosion attack. For this purpose there are two essential ways possible: Firstly, an increase of the corrosivity of the medium, for example, by lowering of the pH value or the other, an increase in temperature, which may correspond generally to an exponential increase in the dissolution of material (corrosion rate).

A further possibility for corrosion measurements are electrochemical measurements, such as the potentiodynamic measurement. With this method, a so-called time dependent current-voltage characteristic curve taken at a working electrode, which in this case represents the sample to be examined. This characteristic curve can be evaluated in terms of the corrosion behavior in different ways: free corrosion potential, exchange current density, potential and current noise and more. These measurements give information about the degree of corrosion of the measured sample. Thus e.g. the dissolution rate of the heat exchangers in waste incineration plants has been investigated. In Figure 1 this is shown at two different positions in the incinerator. Knowledge of the corrosion rate provides important information for the operator of such a plant.

Electrochemically measured corrosion rates, measured in the waste incineration plant

Contact Person:

Matthias Klemm