How to Paint Concrete that Has Already Been Painted
It's easy to paint concrete. Concrete surfaces are common in households, especially on exterior walls and surfaces surrounding the home. Even though it’s rough texture makes it a piece of cake to get fresh paint to adhere to untouched concrete, every so often your concrete need to be touched up with a fresh coat of new paint, which is a bit more challenging.
Repainting concrete surfaces is a bit more demanding than painting freshly-laid concrete. Aged concrete surfaces are coated with various things, such as staining compounds, sealants, and of course older paint, all of which present difficulties.
Here's how to update your worn-down concrete the correct way.
Step 1 - Cleaning and Scrape
Prepare a solution of water mixed with any household cleaning chemical. Scrub the surface with a long-handled brush. Allow the concrete surface to dry.
Existing paint needs to be scraped and sanded. Scrape any areas with loose or flaking paint, and lightly sand using fine (120 grit) sandpaper. Lightly sand intact areas of paint as well to give them the grit needed to receive new paint.
Clean the surface with a dry mop.
Step 2 - Buff the Concrete Surface
Use a floor-buffer for scuffing away the loosened spots of paint. You can rent a floor-buffer from a hardware supply store. Allow the cleaned surface to dry. A moist surface isn't ideal for further cleaning or painting.
DISCLAIMER: A floor buffer is a fast-moving, high-powered machine. While models will vary, be safe and follow all instructions that accompany your device.
Step 3 - Removing Curing Compounds
Inspect the dried concrete surface for curing compounds. After the buffing, the curing compounds are revealed in the form of small spots below the old paint. Prepare a solution of denatured alcohol and hydrated lime in equal proportions.
Mix the contents using a plastic spatula until it develops a paste-like consistency. Apply this paste on all the visible spots. Give the paste time to dry until it hardens into a thin crust. Scrape-away the dried spots with a bristled brush and sweep up the chips with a broom.
Step 4 - Preparing the Epoxy Paint
A tough, strong surface like concrete is best covered with a specialized variety such as a coat of epoxy paint. Since epoxy paint is sold as two disparate, stable ingredients that are then mixed into a temporarily usable paint, preparation is needed at this stage as well since once mixed the paint should be used immediately.
When using epoxy paint, only mix enough of the two parts of the product to be used immediately. Epoxy paint cannot be stored once the two parts are mixed, and any leftover must be disposed of properly. The best way to dispose of epoxy paint is to leave it in an open paint can and let it dry out until it becomes a solid. It can then be thrown away with normal household trash.
DISCLAIMER: A respirator MUST be worn when using epoxy paint. Additional protective gear such as safety goggles is also advised. Exposure to the chemicals and fumes in the epoxy paint can be dangerous and toxic.
Step 5 - Painting Prepared Concrete Surface
Start by painting the edges of the concrete surface. Use a bigger paintbrush for this. Use the paint roller for painting the areas away from the edges. Allow the first coat of paint to dry for about 10 hours. Apply the second coat after the interval. Allow the paint to dry for about five days. On the sixth day, inspect the color of the paint. If the desired shade is missing, apply another coating.