How is adhesion improved
Adhesion or bonding primers chemically bond with the substrate to increase adhesion and form a strong bond between the substrate and the coating.
Primers for coatings
Bonding primers seal the concrete surface and create an adhesive surface for a coating to bond to the substate. Concrete itself isn’t the best substrate for holding coatings because of its high porosity and alkalinity. Without a bonding primer there is nothing for the coating to grab onto. If concrete is not properly primed the topcoat is at risk for failure. On exterior applications, a water repellent sealer is an excellent bonding primer to prevent moisture intrusion from delaminating a coating. In addition to sealing a porous substrate and adhering to the topping, primers increase the wettability of the topcoat making it easier to spread, thus increasing the working time, and decreasing the risk of a fisheye effect. Epxoy primers are often used prior to the application of urethane topcoats as urethane don’t like the alkalinity of the concrete so they will try to repel it. By using an epoxy primer the urethane is bonding to the adhesive primer.
Primers for sealers
Concrete densifiers are excellent options for hardening concrete; however, they provide no protection from water, deicing salt exposure or surface staining. They are however excellent primers to use prior treatment with a penetrating, water repellent sealer. They will help to densify the concrete making it less permeable and will also promote adhesion through the chemical bonding process.