You CAN stain concrete.

More Info: Because concrete is porous and naturally light in color, the acid stains that are used in concrete staining easily react with the concrete's surface causing a permanent color change.

How Acid Stains Work

In order to stain concrete successfully and permanently, you need to use a special acid stain that actually penetrates and slightly etches the concrete.  Acid stains are chemically reactive with acid based coloring dye containing water, hydrochloric acid, and metallic salts.  Once the acid stain is brushed onto any concrete surface, it will penetrate through the pores and react with the calcium hydroxide present in the concrete.  Because the stain is chemically reacting with the concrete, it becomes a permanent part of the structure and will not fade, peel, or chip like regular paint.

How to Surface Prep Concrete for Staining

Anything that is currently on the surface of your concrete must be fully removed to allow the stain to absorb the concrete surface successfully.  This is especially important if there have been any oil or grease spills.  A trick to identify spots where stain won't penetrate is to throw water on the surface. Areas where there is not penetration will need to be addressed.

Specific removal methods will depend on the stain or imperfection but include stripping, sanding, applying solvents, grinding, or simply scraping the surface of the concrete.  Ensure that the cleaner or solvent you choose for the job will not leave a residue while using a stiff bristled brush or a pressure-washer.