Coating failures are typically caused by inadequate surface preparation. For a coating to bond properly, the concrete surface must be sound, clean, free from surface defects and dry. The surface should also be properly roughened to establish a good mechanical bond. Failure to properly prepare the surface typically results in adhesion failures or the coating separating from the concrete, wasting both time and money.
Before applying a decorative or protective coating to a vertical or horizontal concrete surface, prepare the surface by cleaning and roughening, repairing defects, inspecting and testing the surface for soundness and cleanness. Because surface preparation requirements vary from one job to the next and for different types of coatings, be sure to read and follow the recommendations provided by the coating manufacturer. Failure to follow the manufacturer’s recommendations may void the manufacturer’s warranty but, more importantly, may cause the coating to fail.
Perform concrete surface survey
Before starting the job, examine and test the surface to be prepared for the presence of debris, dust, dirt, oil, grease, laitance, mortar splatter, efflorescence, curing agents, sealers and other contaminants. Any of these will prevent the coating from properly bonding to the concrete.
Test concrete for oil, grease, curing agents and sealers by performing a water absorption test. Place a few drops of water on the concrete. If the water beads up, then a surface contaminate exists. If the water absorption test is inclusive, place a few drops of diluted muriatic acid on the surface. If there is no visible reaction (foaming), then a surface contaminate exists. Next, try to determine the depth of the containment by progressively sanding or grinding the surface until it freely absorbs water or a reaction occurs with drops of acid. If […]