The role of a primer is to seal the porosity of the surface (over a porous surface) and to improve the adhesion mainly over a smooth and non porous surface. Good adhesion of a system is obtained by a combination of both chemical and mechanical adhesion (for example anchorage over a porous surface). Mechanical adhesion over a gloss and smooth surface is always difficult to achieve, however can be improved by abrading that surface.

The most appropriate primer for each individual project depends on the type of surface, specifications and requirements of that project.

Adhesion tests are always recommended for each project. Compatibility between the primer and the surface material has to be checked. (For example Humidity Primer cannot be applied over a surface that was previously treated with hydrophobic additives).

Previous treatment of the surface is always recommended to increase the mechanical adhesion of the primer over the surface. Diamond grinding over concrete, abrade non porous surfaces.