On-line corrosion monitoring in district heating systems

Sonja Richter, R.I. Thorarinsdottir, Lisbeth Rischel Hilbert, Antero Pehkonen

    Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review


    Traditionally corrosion monitoring in district heating systems has been performed offline via weight loss coupons. These measurements give information about the past and not the present situation and require long exposure time (weeks or months). The good quality of district heating medium makes corrosion monitoring a challenge. Under normal conditions the pH is high (app. 9), conductivity is low (app. 10-200 µS/cm) and the concentration of dissolved oxygen is negligible. The low corrosion rates (in the order of µm/y) are difficult to measure and furthermore, factors such as hydrogen sulphide complicates the chemistry of the environment. Hydrogen sulphide is present in geothermal systems and can be formed as a by-product of sulphate-reducing-bacteria (SRB). The application of electrochemical methods makes on-line monitoring possible. These methods include: Linear Polarization Resistance (LPR), Electrochemical Noise (EN) and Zero Resistance Ammetry (ZRA). Electrochemical Resistance (ER) has also been used to measure corrosion. The method traditionally only measures corrosion off-line but with newly developed high-sensitive ER technique developed by MetriCorr in Denmark, on-line monitoring is possible. In order to assess both general corrosion and localized corrosion, it is necessary to apply more than one monitoring technique simultaneously, ZRA or EN for measuring localized corrosion and LPR or ER for measuring general corrosion rate. The advantage of monitoring localized corrosion is indisputable since 70-90% of corrosion damages are the result of localized corrosion such as e.g. pitting or crevice corrosion.
    Original languageEnglish
    Title of host publicationThe 9th International Symposium on District Heating and Cooling 2004
    Publication date2004
    Publication statusPublished - 2004
    Event9th International Symposium on District Heating and Cooling - Helsinki University of Technology, Espoo, Helsinki, Finland
    Duration: 30 Aug 200431 Aug 2004


    Conference9th International Symposium on District Heating and Cooling
    LocationHelsinki University of Technology
    CityEspoo, Helsinki


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