The concrete sewage settling tank is to be renovated. A poorly adhering cement grout was found on its inner surface. Expected loads: sewage temperature in summer approx. 313 K (40°C), Winter 193 K (20°C); waste water contains mainly acids (acetic acid, salty, sulfur and fatty acids), salts of these acids and chlorine derivatives of hydrocarbons. Please list the steps involved in applying the coating to the concrete sludge tank and the materials used. These steps are as follows:
1) rubbing the concrete with furnace slag and blowing it with oil-free air;
2) colorless priming, diluted epoxy resin;
3) application of the first layer of solvent-free epoxy varnish;
4) application of a second layer of solvent-free epoxy varnish;
5) application of a top layer of solvent-free epoxy varnish.
The minimum thickness of all layers must be 300 µm. If this thickness can be achieved with fewer layers, and the contractor is able to achieve it, then the coating may consist of a correspondingly smaller number of layers. On the primer layer of epoxy resins, it is also possible to make a coating of polyurethane varnishes. Polyurethane varnishes are even more acid-resistant, but the acid resistance of epoxy paints is sufficient for this type of load, especially when the coating is cured with isocyanate.