Oily Residue

February 28, 2018

What’s this oily residue on the surface that I treated with ice melter?

This question comes up often from users of our calcium chloride and/or magnesium chloride product groups.   Calcium chloride and magnesium chloride are high performance deicing products that are very effective at managing snow and ice across all temperature ranges.   Both chemical compounds, MgCl2 and CaCl2, are hygroscopic.   That means that these products attract water and are trying to take on enough water to satisfy their natural hydration points.

When you treat a surface with either calcium chloride or magnesium chloride, if it does not snow or there is more product applied than needed, it will continue to draw moisture from the atmosphere and form a brine.  These brines can be oily feeling and when they form on polished surfaces such as granite, tile, or linoleum floors they can be very slick and must be properly managed to prevent surprises from people crossing those surfaces.   While this is uncommon, it is not rare and understanding that these performance deicing products, as well as any product containing these two performance compounds, can draw moisture and create an oily film.  The oily residue can be slippery on smooth floors (a potential hazard) and can attract dirt on carpets.

The images below illustrate how premium deicers will draw moisture from the air and hydrate when there is no snow.   This is the desired effect of anti-icing where treatment before a snow storm creates a brine to melt the first snowflakes and prevent them from freezing to the surface.

The best way to prevent ice-melter problems like this is to not over-apply the product and to prevent it from being tracked into the building. Use walk-off matting both outside and inside all entrances and clean them with a mop or vacuum throughout the day.  We recommend that all facilities, as a matter of practice, triple walk-off matting during snow and ice events.   The added mats will aid pedestrians in remembering to clean their feet.

A pylon sign stating to “Please wipe your feet” will also help.   Once the winter event is over and the deicers are down, then roll up the extra matting and save it for the next event.   The additional matting change from normal is something that all pedestrians will notice because it’s a change and related only to inclement winter weather.

In some cases, unsealed poured concrete and concrete pavers will trap these brines in their air voids within the concrete and may hold a darker color and appears “wet” or even oil stained.  The surface is not stained and water (or more snow) will quickly wash away that residue.

How to remove the residue?

The easiest way to remove excess brine residues is to prevent them from forming to start with.   That means apply what is necessary to effect safe and clear walkways, and, broom off excess deicers so that they are not tracked into the building.   If they are tracked in on a polished surface, then wet mopping with only water is the easiest way to quickly remove any formed residue.  If on a carpet, then wet-vacuuming the carpet will also remove accumulated brines and power washing for outdoor residue IF you wish to remove it which may remove the anti-icing application for the next storm.

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