The Cause
Flaking paint on concrete patios is often caused by lack of proper cleaning during the preparation and bonding processes. Excessive moisture is also a cause, particularly with patios that are installed on ground level without a proper moisture barrier being applied. To inspect for excessive moisture, cover the suspected area with plastic tarp and secure it in place with tape or weights. Allow it to sit for two days and then inspect the concrete for signs of discoloration and moisture. If these exist, you will need to locate and repair the source of moisture before continuing. It is also important to note that older concrete patios will naturally flake and along with the concrete comes the paint. Another cause of flaking is the application of oil-based paints on an unfinished, unetched, or uncured concrete surface. When the concrete patio is not properly prepared for paint, the concrete alkaloids react with the oil-based components of the floor coating, a process called saponification, and create a soapy type of film that prevents the oil-based paints from properly adhering to the surface of the concrete, therefore leading to flaking.
Repairing the Concrete
Your first step to repairing the concrete is to remove all the layers of flaking paint from the surface. Using a wire brush or sand blaster, remove any evidence of paint from the surface. Using a trisodium phosphate (TSP) cleaner, available at your local home improvement store, thoroughly clean any residues, grease and dirt from the surface of the concrete. Be sure to vacuum all the remaining water from the surface to prevent water absorption into the concrete that will again cause flaking and peeling of the paint layer. You will need to use an acid etching compound to create a rough and porous surface on the concrete for an adequate bonding surface. Be sure to follow the manufacturer’s directions exactly to prevent damaging the concrete surface. After you have etched the concrete, you will again need to vacuum up any residual moisture and chemicals left after the etching process.
Refinishing the Concrete
You will need to purchase and apply a quality concrete sealer to the masonry before beginning the repainting process to prevent any more moisture from seeping through the concrete and interfering with the bonding process. Allow the sealer to dry and apply a second coat if necessary. Then follow up with a quality coat or two of masonry primer. When purchasing paints to refinish the concrete patio, be sure to buy paints designed for outdoor masonry floors. If necessary, purchase an additive to create texture in the paint. When applied to paint, the additives create a slip-resistant surface on the concrete, preventing slips and falls. Apply paint in thin layers, allowing each coat to cure completely before proceeding to create a hard, durable surface that will prolong the life and appearance of the concrete patio.