Biogenic sulfuric acid corrosion

Revised DIN 19573 Standard: Biological method supplements testing of mortars in drainage systems for resistance to sulfuric acid attack

Press release /

Building material manufacturers and facility operators face the challenge of using materials with high long-term durability. Particularly in sewer construction and wastewater systems, biogenic sulfuric acid corrosion (BSC) can severely damage mortar and concrete and result in high remediation costs. The revised DIN 19573 standard for cementitious-based mortar in drainage systems now takes this into account more thoroughly: In addition to the chemical acid test, it describes a biological method that accounts for the microbiological processes involved in biogenic sulfuric acid corrosion. At Fraunhofer UMSICHT, materials can be weathered according to this method in a way that simulates real-world conditions and accelerates the process.

© Fraunhofer UMSICHT/Mike Henning
At Fraunhofer UMSICHT, materials can be tested and weathered using a new biological method to simulate exposure to sulfuric acid in an accelerated manner.

Mortar used in sewer lines or wastewater treatment plants must be particularly resistant to biogenic sulfuric acid. This acid can severely corrode the material and, in the worst case, completely destroy it. The cause is an interplay of biological and chemical processes: Bacteria first form sulfide from sulfur-containing substances in the wastewater, which then produces hydrogen sulfide (H₂S). The gas rises into the air space of the sewer and deposits on material surfaces. There, it undergoes further chemical reactions until sulfuric acid is ultimately formed. This acid corrodes mortar and concrete.

The DIN 19573 standard

With the publication of DIN 19573 in March 2016, a German application standard for cementitious-based mortars was issued for the first time in the history of sewer construction. It clearly defines test procedures to assess the suitability of mortars for sewer construction and sewer rehabilitation. Annex A describes a test procedure to demonstrate resistance to biogenic sulfuric acid corrosion for the then-new mortar class XWW4. This test procedure uses synthetic sulfuric acid, which is why it is also known as the “acid bath test.”

However, the method cannot account for the biological component of the damage process – the metabolic activity of microorganisms or how it is influenced by the material used. The revised DIN 19573, published in June 2026, therefore introduces a biological test method in Annex D (informative). While it is not currently mandatory, it offers manufacturers and operators an additional means of evaluating the suitability and durability of their materials under realistic conditions.

Fraunhofer UMSICHT has nearly 20 years of experience in this field and, together with its microbiology partner, Dr. Brill + Partner GmbH Institute for Antifouling and Biocorrosion in Hamburg and Bremen, has incorporated this expertise into standard. Since 2006, facilities have been in operation at the Fraunhofer UMSICHT site in Oberhausen that simulate biogenic sulfuric acid corrosion in a realistic, time-compressed and reproducible manner. In the BioThio® facility, materials can be tested and further developed under accelerated conditions using hydrogen sulfide and sulfur-oxidizing bacteria in controlled environmental conditions.

BSC-resistant materials

“The biological process provides a solid foundation for characterizing materials under conditions that realistically simulate biogenic sulfuric acid corrosion. It thus offers manufacturers opportunities to specifically improve the quality and durability of their materials,” explains Holger Wack, group manager of Building Materials at Fraunhofer UMSICHT.

Against this backdrop, a working group within the European Committee for Standardization (CEN) is currently working on the development of a European standard.

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