While polyureas can be formulated with some remarkable physical properties including enhanced adhesion, as mentioned before, there is rarely a successful polyurea application that does not include proper surface preparation and testing.
In addition to proper surface preparation procedures and techniques, the use of primers is strongly recommended in most applications. You should always consult your material supplier for the best compatible system/primer combination for each particular substrate.
Concrete should cure for a minimum of 28 days at 70°F (21°C). Hydration still continues even afterward, so the longer you wait, the better. You should always test the moisture content and vapor transmission to assure the concrete is fully cured, adequate surface conditions exist and that proper system adhesion can be achieved.
Concrete systems often require vapor barriers or other means of waterproofing to prevent water intrusion, which can ultimately lead to delamination and failure of the coating system. All grease compounds and other foreign matter on the surface should be removed by sandblasting, shot blasting, mechanical scarification or suitable chemical means. These removal methods along with controlled standards as provided by PDA, SSPC, NACE, and ICRI are used to clean and decontaminate the concrete surface.
Cracks in the concrete should be routed and filled with an appropriate compatible material to the primer system. Any bug holes or pin holes should be filled in the same manner. Any sharp or rough surfaces should be ground to avoid protrusions. The concrete surface should also be prepared with a grip enhancing profile to aid in proper adhesion of the primer and polyurea system.
Steel surfaces must also be free from rust, salts, dirt and any other contaminants. Any welds shall be free of voids and spurs and sharp protrusions should be ground smooth. Be sure to test the surface conditions prior to application of the primer and polyurea system.
The steel surface should be blasted to near white finish and left with a 3-4 mil profile to create a surface finish for the polyureas and primers to chemically and mechanically adhere to. The SSPC has a spec for steel preparation that should be followed.