coatings and adhesives require different surface preparation depending on the substrate

Primer is not the same as primer and is not the same as the term bonding agent, although they are often used synonymously. Primers and undercoats, however, fulfil different tasks in coating and bonding processes. They are often different in terms of material and not comparable in application.
Primers improve adhesion on critical substrates enormously. In many cases, a permanent bond between coating or adhesive and substrate is only possible with the right primer. Ideally, they act as a chemical coupler (special primer) and enable bonds between substrate and coating or adhesive with enormous strength. However, such primers are usually not binders in the classical sense and do not form films!

The function of a bonding agent, on the other hand, is different. Also called deep primer, basecoat, these designations already describe the application in the approach.

Specifically adapted to the substrates, bonding agents strengthen and harden the substrate, bind fine dust to the surface, fill pores, block and isolate moisture, pollutants, etc..
In most cases, these products are made of binders that are chemically similar to (or at least compatible with) the subsequent coatings, are sufficiently thin and contain no or only small amounts of fillers and pigments.

An important and often insufficiently considered function of a bonding agent coating is pore closure. Sufficient filling of the pores prevents the formation of pinholes or pinholes in the surface of a coating, caused by burst bubbles of air that migrate from the pores through the fresh film to the surface.

On porous, absorbent substrates without a bonding agent, part of the binder of a coating migrates into the pore structure of the substrate. Solids remain behind because of the size of the particles (a filter effect of the pores).
At the interface between coating and substrate, this leads to a binder depletion of the coating. Typical consequential damages are adhesion problems. Properly formulated primer coatings prevent this damage.


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  • Special Primer For Polyurethane And Epoxy Coatings