Protection and rehabilitation of existing concrete tanks

Why does concrete corrode in biogas tanks?

Sulphuric acid can form on moist concrete surfaces in the gas zone and attack the cement paste that binds the concrete together.

Where does the acid form?

Hydrogen sulphide (H₂S) produced during anaerobic digestion enters the gas space. Where moisture and oxygen are present on the tank wall, sulphur-oxidising microorganisms can convert it into sulphuric acid. This acid weakens the concrete and causes material loss.

Is the damage only superficial?

The visible surface does not reveal the full depth of attack. Chemically affected concrete can extend beneath it. The depth and condition of this damaged zone determine the preparation and repair work required.

Read the technical explanation

Why does the concrete surface matter for coatings?

A fully bonded coating needs sound, clean and properly prepared concrete. The moisture level must also meet the coating material's application requirements.

What needs checking?

Surface strength, chemical contamination, moisture, condensation and temperature all affect the quality of the bond. Even a chemically resistant coating cannot provide reliable protection if it loses adhesion to the concrete.

What changes with mechanical fixing?

A mechanically fixed lining is anchored in the concrete instead of relying on adhesion over the entire wall. The anchors must extend beyond the damaged surface zone into concrete capable of carrying the required loads.

Compare the substrate requirements

Which rehabilitation methods are available?

Available methods include mineral systems, epoxy and polyurethane coatings, rubber linings, fibre-reinforced systems and thermoplastic linings. Their suitability depends on both the exposure and the way they are installed.

What determines suitability?

Chemical resistance, temperature and mechanical loads must be considered alongside the condition of the concrete. Joints, pipe penetrations, surface preparation and the available shutdown period can be decisive in selecting a method.

The method comparison explains these differences. TP·VAS uses mechanically fixed PP-H plates and flexible FPP cover strips to form a welded protective lining.

What happens when a tank expands and contracts?

Sunlight, shade and the change between daytime heat and night cooling cause temperature differences and movement in the tank wall. The protective system must accommodate this movement.

Fully bonded versus mechanically fixed

A fully bonded coating follows movement of the concrete and must accommodate the resulting stresses. A mechanically fixed lining allows relative movement between the plates and the wall. Its fixing details and flexible connections must also accommodate the expansion and contraction of the plastic itself.

Read about thermal movement

What determines rehabilitation downtime?

Cleaning, concrete repairs, surface preparation, drying, installation and curing together determine how long the tank must remain out of service. Access and the extent of damage affect each stage.

Why can mechanically fixed plates be faster?

The plates require no full-area adhesive bond, so the wall does not have to be dried and prepared for that purpose. At Haus Düsse, cleaning with a conventional pressure washer was sufficient before installation. Welding surfaces must be clean and dry, and local sealants require their specified application and curing conditions.

Read about installation conditions

What is needed for an initial project assessment?

Send the tank dimensions, construction type, contents, operating temperature, known damage, photographs and project location. Existing drawings and inspection reports are also useful.

What happens next?

We review the information, identify suitable methods and clarify any missing measurements or investigations. From this, we develop the proposed scope of work, connection details, material requirements and approach to installation.

See the information checklist below