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Salt stains come from a few sources:

• Road salts are carried onto your driveway from the tires. Salts are mixed in with water and when the concrete absorbs the water, it absorbs the salts with it. Water evaporates and salts are left on the surface and in the pores.
• De-Icing salts are applied to the driveway. The salts melt the ice into water and water carries salts into the concrete. Water evaporates and salts are left on the surface and in the pores.

Salt does more than just stain a driveway. Salt is responsible for causing a variety of other issues including surface spalling. Salt caused ice to melt and the concrete will absorb the water from the melted ice. When the water is in the pores, it will refreeze. Ice takes up more volume than water so when the water turns to ice within the pores, it causes the pores on the surface to crack open and make room for the expansion. When the surface pores break open, you get spalling.

The first step is to remove salt stains from the driveway. This can be done with a pressure washer and mild cleaning solution, or with an acid based solution and stiff brush. How you clean the driveway will depend on what you have access to for materials, and what you are more comfortable with working with.

Once the driveway has been cleaned, it is important to seal the driveway.

There are two types of sealers that can be used. The best sealer being a penetrating water repellent sealer, like a high solids silane siloxane. Silane siloxane sealers, like the Armor SX5000, will seal the concrete from within the pores. Water will bead off the surface, preventing salt water from being carried into the concrete. Salt will be left on the surface where it can be easily swept away.

The second type of sealer that can be used is an acrylic sealer. An acrylic lacquer, solvent based, is ideal if you are looking to change the look or color of the concrete. Acrylic sealers are often available in different colors and levels of gloss.