Concrete is porous and paint doesn't adhere well. To ensure good adhesion, the concrete surface must be sealed.
This is a relatively simple and inexpensive task that can be done at home or on our own with the help of some products that are available in stores. When preparing concrete it's also very important to clean the concrete floor with rubber gloves from any grease and dust particles before applying any sealer. For proper preparation of the concrete floor for painting you need the following materials.
Wire brush
Sandpaper (medium grain)
Water hose
Bucket and rubber gloves
Rags and sponge
Screwdriver and putty knife
Paint roller and pan or brushes and rollers. You can choose between oil base paint or water-based paint, but always chose paints made specifically for outside use.
Water sealer or concrete paint
Rubber gloves
Stiff bristle broom
The first step to prepare concrete for painting is wire brushing or using a pressure washer to wash off any dust, dirt, or debris that are present on the concrete dry surface. Make sure you have cleaned it up properly before moving to the next step. If some parts are covered with existing paint, old paint, grease, or oil stains, then use a fresh water hose, power washer, or a heavy-duty concrete degreaser or high-pressure cleaner provided by most homeowners to clean them out properly and leave it to paint dry for a day before continuing with the rest of the steps with safety goggles, masking tape and adequate time.
Use medium-grain sandpaper (120 grit) for the wall and edges, wet it thoroughly with clean water and debris, and go over all the cleaned areas with this sandpaper until you completely remove any gloss from these areas. After this, make sure to wash the concrete floor for any sand residue with water as in plastic watering.
For the best result it's recommended to do this step twice while you prepare your concrete for painting, so for the first time pass over it using medium grain sandpaper (120 grit), wait until all the residues and trapped moisture are removed then wet it thoroughly with water again and go over the previously cleaned areas once more, but this time use fine-grain sandpaper (180 grit). Make sure there isn't any gloss on these areas after you're done.
If necessary, use a putty knife or scraper to remove any oil residue that might be present on some of these areas. After removing them make sure you clean the concrete floor with a pressure wash before continuing with the rest of the steps.
Use a damp rag or sponge to wipe off any remaining dust from the concrete. The surface must be completely dry and free of any grease or sand residue.
You can successfully paint concrete surface/floor by applying the first coat of water-based sealer over the entire prepared concrete floor area, letting it dry completely for 24 hours before beginning with the next step. Make sure you choose a sealer that's made specifically for outside use because these products contain ultraviolet filter agents that protect them from deterioration caused by exposure to direct sunlight and moisture.
If your sealer is specifically formulated or oil-based then wait until it dries out completely and apply a second coat of acrylic latex primer over the painted surface using a brush, roller, or spray gun. This should be applied very thin and all residue should be removed as you go.
Yes, you do need to prepare concrete for painting before you apply the first coat. In addition to that, it's highly recommended to clean the area properly for any stains or grease with clean water before your prepare concrete, from any dirt and dust particles with a heavy-duty concrete degreaser before applying any sealer. These surface contaminants can affect the adhesion of paint so they should be cleaned thoroughly. Also, make sure there are no oil residues on the surface after you clean it because these types of paint peel off more easily when they're applied over concrete that has oily residue.
No, you don't need to acid etch your concrete floor before a paint job. Deep-cleaning processes such as using muriatic acid are necessary for older and more porous types of surfaces because they remove any dirt or residue that might remain on them. However, this method is not suitable for seal coating or when it comes to areas where the surface has been previously painted because acid washing removes all its previous coats of paint which weakens its adherence attributes If you have painted over an oily surface or have oil stains then make sure to sand it down with sandpaper to clean away any oil residue. It's also recommended to use a primer coating over these areas for better adhesion purposes because primers provide a strong base for paints.
Below is a list of the best paints for concrete floors.
These types of paints are suitable for interior surfaces because they have low toxicity levels so they don't affect indoor air quality when used inside homes, offices, and schools. They also give you more time to clean up spills compared to other types of concrete paint so it's easier to work with them on most surfaces.
Latex-based paints are more suitable for smooth and nonporous exterior surfaces and bare concrete surfaces because they don't accumulate dust particles that easily. They're also inexpensive, easy to use, and durable which makes them perfect for both interior and exterior surfaces which is why they're one of the most popular types of paint used today.
Painting such surfaces is a skill in itself, which you can get more information on at training.gov.au.