The effluent tank as part of the new development required a tank lining to protect the concrete from hydrogen sulphide and biogenic sulphuric acid. Hydrogen sulphide gas is produced by effluent breaking down, which when in contacts water forms biogenic sulphuric acid which is highly corrosive to concrete.
We proposed the application of a proven tank lining used extensively in waste water applications in the form of Remmers Epoxy Universal. What makes this tank lining particularly suitable for this application is that Remmers Epoxy Universal is a crack bridging epoxy tank lining, perfect for lining concrete tanks.
All surfaces to be coated were first prepared by method of vacuum controlled diamond grinding to remove surface laitance and contaminants in order to provide a clean and sound surface for the tank lining to adhere to.
When applying tank linings to concrete an issue that must be addressed is the filling of blow holes in the concrete – this cannot be filled with tank lining materials alone.
A cementitious fairing coat in the form of Remmers WP Sulfatex was applied by slurry brush, trowel and sponge float in order to provide an excellent mechanical profile for the epoxy tank lining to adhere to. Most tank linings require a surface roughness in order to gain proper adhesion.
The fairing coat was allowed to hydrate naturally and the completion of this confirmed through moisture testing of the substrate using a Tramex Concrete Moisture encounter gauge as part of our standard quality assurance.
Climatic conditions were tested and recorded with regard to relative humidity and dew point again as part of our standard quality assurance. Ensuring the correct climatic conditions is essential when applying tank linings as if these are not respected the tank lining is effectively being applied to a film of moisture which will prevent proper adhesion and ultimately lead to premature failure of the tank lining.
All surfaces were primed using Remmers Epoxy MT100 damp tolerant epoxy primer applied by method of brush and roller. This versatile primer can tolerate substrate moisture content of 6%, reducing hydration periods required prior to the application of the tank lining.
Following priming Remmers Epoxy Universal was applied in two coats of contrasting colour as per best tank lining practice. The thickness of these coats was checked using wet film thickness combs again as part of our standard quality assurance.
Following cure of the third coat in the tank lining process the cured epoxy lining was checked for porosity using a DC Holiday spark tester. By running a high voltage/low current energised copper brush over the surface any breaks or ‘holidays’ in the tank lining are identified by a small spark and an alarm on the unit. This is why this process is also commonly referred to as ‘spark testing’.
A single pin hole is a point of failure in a tank lining as it allows aggressive agents such as biogenic sulphuric acid to reach the concrete and allow corrosion to commence.
