How to Paint Concrete that Has Already Been Painted

It is rather easy to paint concrete using some well-guided information and basic, household supplies. Concrete surfaces are among the most common form of household surfaces. Like other domestic surfaces, concrete also ages and needs a periodic coat of fresh paint. To paint concrete that has already been painted before, please consider the following information.

It should be noted that repainting concrete surfaces is a bit more demanding than painting freshly-laid concrete surfaces. This is because you need to prepare the concrete surface in a specific manner. Aged concrete surfaces are coated with various things, such as staining compounds, paints and sealants, that can pose problem for the fresh paint. Surface preparation includes de-greasing and de-staining the surface. Various chemicals are available in the market promise to prepare a previously-painted concrete surface with a single application. However, such chemicals can be very expensive and are seldom used for household application. The more prudent approach is to prepare the concrete surface using a combination of some basic techniques.

Step 1—Basic Cleaning & Stripping

Prepare a solution of water mixed with any household cleaning chemical. Use this solution for cleaning the concrete surface. It is better to scrub the surface with a long-handled brush. Allow the concrete surface to dry. Identify the patches on the concrete surface where the paint seems to be intact. With a putty knife or utility knife, scrape such spots. Use a chemical stripper for removing the remaining patches of paint. Apply the chemical stripper as per the packaged instructions. Clean the surface with a dry mop.

Step 2—Buffing 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. Please note that a moist surface isn't ideal for further cleaning or painting.

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 actual paint. Prepare a solution by mixing denatured alcohol and hydrated lime in equal proportions. Mix the contents using a plastic spatula into a paste-like consistency. Apply this paste on the detected spots. Allow the paste to dry into a thin crust. Scrape-away the dried spots with a bristled brush. Clean the surface with a broom.

Step 6—Applying Primer

Most epoxy paints require a primer application. The primer is applied before applying the epoxy paint. Mix the primer according to packaged instructions. Coat the cleaned concrete surface with the primer. Use a paintbrush for this purpose. You can also use a paint-roller for speeding through this part. Allow the primer to dry for about 24 hours.

Step 7—Preparing Paint to Paint Concrete

Most branded epoxy paints need to be mixed with some chemicals before application to maintain the right consistency and color density. Mix the paint with the retailed additives, according to packaged instructions.

Step 8—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 area 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 5 days. On the sixth day, inspect the color of the paint. If the desired shade is missing, apply another coating.