Mag Chloride on Denver Roads: Protecting a Coated Garage Floor This Winter

Every winter, Colorado road crews spray liquid magnesium chloride on highways and major streets ahead of storms. It helps keep ice from bonding to the pavement, and it works. It also clings to your tires, your wheel wells and the underside of your car, and drips off onto your garage floor every time you pull in.

If you have bare concrete, that residue is one of the reasons Denver-area garage floors pit, flake and stain over time. If you have an epoxy or polyaspartic coating, it is far better protected, but it still pays to understand what mag chloride does and how to deal with it.

What mag chloride does to concrete

Magnesium chloride is a salt. As it dries on a floor, it leaves a white, sticky film. On bare concrete, salts soak into the surface along with meltwater. Through repeated freeze-thaw cycles, which the Front Range has plenty of, that moisture and salt can contribute to surface scaling: the shallow flaking and pitting you see on older garage slabs and driveways.

Bare concrete is porous, so it also absorbs stains from the dirty slush that comes off vehicles. After a few winters, many garages have a permanent tide line where cars park.

Why a good coating helps

A properly installed epoxy or polyaspartic system seals the top of the slab. Meltwater and salts sit on the surface instead of soaking in, so they can be cleaned away. That is one of the biggest practical benefits of coating a garage floor in Colorado.

The key words are "properly installed." A coating only protects concrete if it is bonded well. Coatings rolled onto poorly prepared concrete can lift, and once water and salt get underneath, peeling tends to spread. Diamond grinding the slab before coating is what gives the system a surface to grip.

What mag chloride does to a coated floor

On a sound coating, mag chloride is mostly a cleaning issue rather than a structural one. The residue can leave a dull, hazy film and make the surface slippery when wet. Left for weeks, the grit carried with it can also scuff the topcoat, especially under tires where cars turn.

A simple winter routine

• Squeegee meltwater out. After a storm, push standing slush and water toward the door or drain rather than letting it dry in place.
• Rinse residue regularly. Every week or two in heavy de-icer periods, mop or rinse the parking area with warm water.
• Use a pH-neutral cleaner. A mild, pH-neutral floor cleaner removes salt film without harming the topcoat. Avoid harsh acids and solvents unless your installer approves them.
• Consider containment mats. A mat with raised edges under each car catches slush before it spreads across the floor.
• Choose a slip-resistant finish. If you are coating a floor now, ask about an aggregate in the topcoat to improve traction on wet days.

What about bare concrete next to the coating?

Many Denver garages have a coated floor but an uncoated apron or driveway outside the door. That exposed concrete takes the full force of mag chloride and freeze-thaw. Sweeping slush off the apron and rinsing it occasionally helps, and a penetrating sealer can reduce how much salty water soaks in. If the edge where the coating meets the apron is chipped, have it looked at, since that is where water most often finds its way underneath.

Spring cleanup

Once the plows stop running, give the whole floor a thorough wash to remove the season's residue. It is also a good time to look closely for any chips or edges that are lifting. Small problems caught early are usually easy to repair; left alone through another winter, they can grow.

Thinking about coating this year?

Winter installation depends on temperature, because coatings need the slab and air within the right range to cure properly. Many installers work through the cooler months with heated garages or carefully chosen products. If you would like to know whether your garage is a good candidate, or what your slab needs before coating, we offer free on-site estimates across Denver, Aurora, Lakewood and the surrounding metro.

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