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     H2S and Corrosion

    Why Coatings Fail

    Why Linings Fail

    What is a Co-Liner™?

    Installation Examples

It is a well known fact that most wastewater structures are made of concrete and steel. Among them are pump and lift stations, wells, sedimentary basins, aeration basins, digesters, sludge storage tanks, collection and conveyance structures, and others.

Concrete is an inherently porous material that allows corrosive liquids and gases to migrate relatively free through its microstructure. In addition, concrete is highly susceptible to microbial colonization.

The aggressive environment found in wastewater structures combined with microbial colonization of concrete causes the gradual loss of structural integrity of wastewater structures.


Traces of structural corrosion and destruction — you can see the steel cage.

Destruction of a sewer structure — the walls and the arch above the sewage water are subject to corrosion.

Spalling of concrete due to corrosion.



Hydrogen sulfide and corrosion cycle

1. Bacteria living in wastewater produce hydrogen sulfide.
2. Bacteria colonizing the concrete surface (Thiobacillus), in the presence of hydrogen and water transform hydrogen sulfide into sulfuric acid.
3. Sulfuric acid attacks the concrete, turning it into gypsum and the concrete looses its structural integrity.



Main tasks of concrete structures
protection and repair:



1. Protection of structures against the aggressive environment found in wastewater structures.

2. Rehabilitation of damaged structures, strength enhancement.

3. Containment of gases and liquids.

4. Infiltration and inflow prevention.

5. Provision of predetermined mechanical and other properties to the concrete structures (visual appearance etc.).