HOW DE-ICERS WORK

THE BASICS

Of the snow and ice melter products available, nearly all are derived from seven or eight materials or blends of these components.  Generally, all de-icing materials work much in the same way:  The must first attract sufficient moisture to form a liquid brine.  This solution then lowers the freezing point of water thus melting ice and snow.

Under normal conditions, de-icers begin by breaking the hydrogen bond that forms when water freezes.  They then dissolve their way downward through the ice or snow until they reach the pavement.  Once there, the accumulating brine undermines the ice to break its bond from the pavement.  When loose, the ice or snow is easily removed.

The ability for de-icers to remain effective depends on the concentration of the brine solution.  Basically, the greater the concentration, the better the performance in melting more snow and ice at lower temperatures.  Some products (like calcium chloride) are greatly affected by the dilution of the brine once the melting process begins, becoming more prone to refreeze at higher temperatures.  For example, at a brine concentration of 10%, a product may be effective to -2^◦ F.  As it dilutes to 5%, it may refreeze at +18^◦ F.  This is why a product may melt very quickly at first then slow down, or completely stop, as its brine concentration decreases.

POTENTIAL DAMAGE TO CONCRETE

A common misconception is that concrete damage occurs because the ice melter chemically attacks the surface.  Chemically, sodium chloride is no more damaging to concrete than is calcium chloride.  In fact, none of the commonly used ice melter materials have any chemical action against concrete.

All concrete contains small micropores into which water will penetrate.  Any damage that occurs is a physical interaction between expanding water as it freezes in the pores of the concrete.  By minimizing the freeze/thaw cycle, de-icers with low melting temperatures also reduce the degree of spalling and surface crumbling that takes place with more frequent freeze/thaw cycles.

Damage to concrete is also minimized by containing the proper air entrainment for the environment where it is used.  These micropores in the concrete increase its strength, thus allowing the use of ice melters at colder temperatures.  Contact your local reputable concrete manufacturer or the Portland Cement Association for details.  Make sure your concrete has cured for a minimum of 1 year to increase resistance to spalling and damage.

PERFORMANCE CONSIDERATIONS

When choosing a snow and ice melter your primary objective is to use a product that will provide maximum performance against accidental falls.

Other issues include:

·        How fast and how long will it work?

·        What is its potential effect on concrete?

·        What is the long-term effect on the applicator?

·        What are the side effects on concrete and vegetation?

·        How does particle size and shape influence the melting capability?

·        What about shelf life and storage limitations?

With all performance variables considered, you’re still faced with the difficult decision of finding the best product for you.  Few will possess the qualities that are most important to you and still fit into the budget.

MELTING SPEED

In today’s fast-paced society, we want products to perform and we want them to work fast under even the most severe winter conditions!  However, some snow and ice melters take longer to work than others.

Generally speaking, the speed at which a de-icer begins to work is determined by its ability to form a brine and is therefore influenced by how rapidly it can absorb moisture.  Temperature plays an important role when comparing melting speeds of various components.  Nearly all de-icers will attract moisture when applied above 25^◦ F.  By contrast, most salt and potassium-based products show little to no ice penetration once temperatures slip down to 15^◦ F or lower.

POTASSIUM CHLORIDE

Potassium chloride is a common fertilizer nutrient that offers more safety to plants and sodium chloride.  Compared to salt this material is not damaging to the soil structure and will corrode metals to a lesser degree.  Potash (KCl) is usually screened and sized for use in granular applications and melts effectively to approximately 20^◦ F.

UREA

Urea is a fertilizer nutrient that can contaminate groundwater and runoff collection ponds with nitrates, a degradation product.  Approximately 10% as corrosive as sodium chloride, urea is Federal Aviation Agency (FAA) approved as an airport runway ice melter (when chloride content is less than 200 ppm).  It is also used near equipment that is sensitive to corrosion by chloride salts (electrical boxes, etc.).  If using near airports or other sensitive areas, make sure the product meets the chloride specifications.  Urea melts effectively to approximately 21^◦ F.

MAGNESIUM CHLORIDE

Magnesium chloride is a very hygroscopic salt.  An open bag will leave a pool of water if left open with the remaining material subsequently becoming hard.  Often used in blends with other chlorides or as a liquid spray solution on concrete surfaces.  Heavy applications can be tracked to indoor surfaces resulting in slippery flooring or oily carpeting.  Magnesium Chloride melts effectively to approximately -25^◦  F.

CALCIUM CHLORIDE

A by-product of chemical manufacturing processes, calcium chloride is a traditional ice melter product.  Very hygroscopic, it forms slippery, slimy surfaces on concrete and hard flooring.  Some people and pets show dermal sensitivity in the form of rashes and “burns”. Handling precautions suggest the use of gloves, goggles, and respirators.  Calcium Chloride melts effectively to approximately -25^◦  F.

CORROSIVENESS TO METALS

Interest in the effect ice melters have on metals, particularly steel and aluminum, has been gaining momentum as users evaluate the long term impact de-icers have on their equipment and surrounding structures.  Several manufacturers have promoted products containing corrosion inhibitors.  These products claim corrosion resistance by coating the target surfaces with a protective barrier.  Of all the de-icers available today, only urea and CMA are recognized as preserving the integrity of metal surfaces.

Corrosion occurs when metal ions combine with oxygen, forming pits or rust.  De-icers containing chloride ions increase the rate at which the oxygen from water reacts to break down metal surfaces.

SIDE EFFECTS TO VEGETATION

Ice melters can affect plants in three ways: salt spray, salty soils, and sodic soils.  Plants vary widely in their response to salts in their environments, with some being very tolerant and some showing no tolerance.

Salt spray damages plants by placing salt on leaves, buds, and bark from the use of snowplows and snow throwers.  This resulting mixture is toxic through extreme desiccation of plant tissues.  Buds that are damaged can prevent the tree or shrub from leafing and flowering the following spring.  Salt can also injure the crowns of non-tolerant and newly seeded turf areas by preventing new shoot and leaf generation the next spring.

Soluble salts in the soil also have a severe impact on plant life.  Even in minute quantities, chlorides are detrimental to the soil microbes that are essential to soil organic matter formation and nutrient availability.  As the concentration of salts increase, they can kill vegetation in much the same way salt spray does…by killing the plant and preventing new growth from occurring.

All soils contain certain amounts of clay particles.  Clay has a negatively charged electrical site that holds onto calcium, magnesium, potassium, and other positively charged elements.  When the amount of sodium on these sites reaches a high level, the clay particles disperse and form a water impermeable layer in the soil structure.

Ice melters containing potassium chloride and urea tend to have less affect on vegetation as both these materials are also fertilizers.  However, over-application of either can cause salt damage.

MELTING TEMPERATURE

Determining the effectiveness of ice melters at certain temperatures depends on the freezing point of the de-icers’ brine and the amount of ice melter in solution.  Some products have definite advantages over others in this area.

The key to understanding a product’s effectiveness begins with determining the test method used to support the advertised performance claim.  While a product may advertise its maximum performance data from the lab (eutectic temperature) significantly different results might appear when applied at the recommended use rate on the package (practical use rate temperatures).

Eutectic temperatures are the lowest temperatures at which brine will still melt ice regardless of how much de-icer is used.  Some de-icers, such as rock salt, may require application rates ten times the suggested use rate to reach their ideal concentration (23%) for maximum performance.  As the solution melts the brine it is diluted and will refreeze again at a higher temperature.

Practical use rate temperatures are a realistic measurement of how a product will perform according to the labeled use rates (usually about one half to one pound of material per one hundred square feet).  Practical use temperatures are those that show obvious melting at a certain temperature within twenty to thirty minutes of application.

TRACKING RESIDUE

Another are of concern is the potential damage caused when an ice melter residue is tracked indoors.  Nearly all de-icers have their drawbacks in this area.  The key is -  understanding how to minimize the residue and to use products with the least damaging affect on indoor surfaces.

De-icers that form a solution will form a residue when the brine dilutes and finally evaporates.  Residues that are water-soluble are usually easy to remove from indoor surfaces by normal water based cleaning procedures.  Try to avoid products that contain clay particulate and high amounts of colorants.  De-icers that are “clean” are less likely to stain, or cause cleaning problems.

Pay particular attention to evaluating the potential volume of ice melted with the volume of material applied.  It makes sense to choose snow and ice melters that require less material to melt more ice at lower temperatures.  Doubling up on the application rate may allow melting to lower temperatures (see Practical Use Rate) but will also increase your product costs and residue tracking.

Another concern in this area is the oily residues left from calcium and magnesium chloride applications.  It should be noted that these materials are also used as dust control agents due to their aggressive sticky nature.  These materials are easily tracked indoors and can be difficult to remove from carpet fibers.  Furthermore, some surfaces can become slippery resulting in other safety concerns.

WORKER EXPOSURE CONSIDERATIONS

HANDLING SAFETY

Safety precautions and over-exposure to hazardous materials in the workplace is a growing concern.  Generally speaking, the primary safety concerns with ice melter ingredients - involves their effect when exposed to skin, eyes, and leather.

Unfortunately, products that claim the lowest melting temperatures (calcium chloride) expose the applicator to greater hazards.  Prolonged or repeated exposure can cause serious side effects that include skin (dermal) burns and eye irritation.  Handling precautions, according to the Material Safety Data Sheet, for calcium chloride include the use of respirators, gloves and goggles when respiratory, skin and eye protection is required.

TRACTION

Recently, in an effort to increase traction, some formulators have added gripping components to their de-icer blends.  Unfortunately, these traction agents are inexpensive forms of sand, gravel or lime and do not contribute to the purpose of ice removal.  In fact, they make removal more difficult as they clog drains and remain piled after the ice has melted.  Furthermore, these materials are easily tracked indoors and, due to their grinding nature, can cause severe damage to hard surfaced indoor flooring or cleaning problems on carpeting.

Copyright © 2002-2008 Golf Enviro • All Rights Reserved