Which product you use to seal your garage floor depends on your reason for sealing, and what you want your garage floor to look like once sealed.
Garage Floor Sealers
A garage floor sealer will penetrate into the concrete and chemically react below the surface. It will not change the look or color of the concrete, and it won't leave behind a surface film or coating. Sealers are great to use if you want a low-maintenance way to seal and protect your garage floor.
Densifiers:Densifiers chemically react to form a crystalline barrier, also known as Calcium Silicate Hydrate (CSH), within the pores. Densifiers will increase the surface strength and density of the concrete. If you simply want to increase surface strength, a densifier is the appropriate sealer. If you want to prevent stains or salt damage, a densifier alone won't cut it - for that, you need a water repellent sealer. If you want to increase the strength and you need water repellency, you can apply a densifier first followed by a water repellent 5-7 days later.
There are two types of densifiers that can be used, a sodium silicate (Armor S2000) based densifier or a lithium silicate (Armor L3000) based densifier. Sodium silicate densifiers are more cost effective but lithium silicate densifiers have an easier time penetrating through dense surfaces. If you have newly poured concrete or trowel finished concrete, consider a lithium silicate to reduce the chance of over application on the surface.
Water Repellent Sealers: Water repellent sealers chemically react to form a hydrophobic barrier within the pores. Once cured, water repellent sealers cause water and other liquids to bead off the surface. By reducing the absorption of water, a variety of issues are reduced including cracking, spalling, pitting, ice and salt damage, and the growth of mold and mildew.
The most common type of water repellent sealer is a Silane-Siloxane blend sealer. Silane-Siloxane sealers take the benefits of Silane sealers and the benefits of Siloxane sealers without the weaknesses. Silane-Siloxane sealers are available mostly in low solids solutions, but some manufacturers offer high solids industrial grade concentrates (such as the Armor SX5000).
Water repellent sealers will reduce stains, including stains caused by oil, by repelling them from the concrete. If oil is left on the surface for more than a couple of hours, stains may form. Water repellent should not be used to stop oil stains, but they can be used to help prevent them.
Garage Floor Coatings
Garage floor coatings will leave behind a protect film, or coating, on the surface. There are several types of coatings that can be used:
Armor UTN60: The Armor UTN60 coating is an industrial grade coating designed to protect concrete surfaces for years to come. The preparation is more intense than a residential grade coating, but the effort is well worth the reward. The UTN60 can last up to 10 years and comes scratch and abrasion resistant, oil and gas resistant, chemical and acid resistant. It is available in several colors and comes in matte, satin, or high gloss.
Acrylic Coatings: The Armor AR350, Armor AR500, and Armor AX25 are the most popular types of acrylic based coatings. While they don't last as long or perform as hard as the UTN60, they will provide an attractive, durable finish that provides protection against stains. Acrylic coatings are popular because they are very easy to apply, and even easier to touch up and maintain.
Epoxy Coatings: Epoxy coatings are a happy-medium between acrylic coatings and urethane coatings. They aren't as easy to apply as an acrylic is, and they aren't as durable as a urethane. They are common, affordable, and easy to apply.