Substrate

Cement bound substrates such as cement screeds or concrete are generally coated, as are magnesia and anhydride screeds, though to a less common extent. If there is a danger of rear moisture penetration, a water vapour diffusion permitting system must be chosen. Thermoplastic substrates, such as mastic asphalt, require a viscoplastic coating.

Primer

As with all reaction resin bound systems, the primer promotes adhesion between the substrate and the coating. The primer usually consists of a solvent free, low viscosity, transparent epoxy resin. The resin primer can be filled with pre dried quartz sands to produce an egalisation layer. Diffusion permitting systems are primed with water emulsified epoxy resin.

Levelling

The discharge resistance of a conductive coating system results primarily from the thickness of the finishing coat. In order to attain an uniform level of resistance over the entire surface the finishing coat must be of uniform thickness. After priming rough and uneven surfaces, it is thus advisable to apply a levelling layer of resin primers and quartz sands.

Conductive layer/Grounding

As the electrostatic discharge capability of concrete declines in the course of time as a result of drying processes, in addition to which the primer acts as an insulating layer, a so called conductive layer requires to be applied. This intermediate layer enables the discharge of electrostatic charges to be cancelled via a conductive layer with a constant level of resistance. The conductive layer consists of two components: The black conductive lacquer and the self-adhesive copper conductive strips. The conductive strips establish the connection between the coating system and the grounding system. The strips are generally applied to the primer or levelling layer in areas which are subject to lower levels of stress and run atleast 30 cm up the wall. As a guide, there should be one connection between the conductive strip and the grounding ring circuit for each 1002 m of floor area.

So called 'conducting sets' offer an alternative and stable means of grounding. These consist of dowels which are fixed to the substrate. a cable lug enables very simple connection to the grounding system. The black conductive lacquer which is rolled over the strips possesses a much higher conductivity in horizontal direction than the coating material.

Finishing Coat

The conductive properties of the finishing coat are generally attained by adding carbon fibers. Numerous different coating systems are available for different applications:

Coatings with electrostatic discharge capability can additionally be gritted to enhance slip resistance. Special silicon carbides with conductive properties are used for this purpose. Fire dried quartz sands are not suitable!

Sealant

Systems incorporating finish coatings which have been rendered conductive by means if carbon fibres possess adequate conductivity to fulfill the requirements for explosion prevention applications. They do not, however, meet the current requirements pertaining to ESD protection. To solve this problem, the finish coatings are additionally provided with pigmented conductive sealants. Such sealants are highly abrasion resistant and possess a certain horizontal conductivity. They are thus able to homogenise the conductivity of the overall system and to discharge arising charges not only vertically, but also horizontally. This capacity ensures compliance with all the relevant ESD standards. Conductive sealant generally consists of water based two component polyurethane or epoxy resin dispersions.