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What's the Difference Between Rock Salt and Ice Melt?

Updated on November 15, 2017
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Melody has volunteered with the CDC and is a member of the Medical Reserve Corps. She brings awareness to public health concerns.

Deciding between rock salt and ice melt is easier once you know the difference.
Deciding between rock salt and ice melt is easier once you know the difference. | Source

What Makes Driveway Ice Melt Best

Rock salt is better at removing existing ice and ice melt is better at preventing ice from forming. The difference between them is that one is a melting agent (de-icer) and the other is an anti-icer.

According to National Geographic, rock salt has been used on roads since 1895. It was not until the late 1980s and early 1990s that ice melt became a popular solution for slick roadways.

You are likely wondering which is best for residential use. Ice melt has become a favorite for driveway applications because its chemical composition is far less likely to cause damage to surfaces than traditional rock salt. Here is what you need to know about how they differ.

Rock Salt vs. Ice Melt

  • Rock salt is not effective on surfaces below 0° Fahrenheit.
  • Ice melt works in below zero temperatures.
  • Rock salt is corrosive to roads, concrete, and metal (your car).
  • An excessive build-up of some types of ice melt may become toxic to the environment (though newer, safer brands are now on the market).
  • Rock salt, also known as Halite, is made from sodium chloride (the same stuff table salt is made of).
  • Ice melt is made from three main types of salt: calcium chloride, magnesium chloride, sodium acetate, and other similar inorganic compounds.
  • Rock salt often costs less money than ice melt.
  • Table salt is virtually the same material as rock salt but is ground so fine that it is much weaker than oval rock salt crystals.
  • Ice melt and table salt differ greatly.
  • Ice melt may be safer for pets.

Rock salt pellets melt ice and is widely used for sidewalks and driveways.
Rock salt pellets melt ice and is widely used for sidewalks and driveways. | Source

Types of Rock Salt

Rock salt is rock salt. No matter which brand you buy there will be little variation other than the size of the pellets. It is made from sodium chloride and is cheap, easy to apply with or without spreaders, and is more traditional.

Example of Rock Salt Brands:

  • Morton's Safe-T-Salt
  • Safe Step 3300
  • The Cope Company Salt

The melting effects of rock salt on an icy driveway.
The melting effects of rock salt on an icy driveway. | Source

Types of Ice Melt

Ice melt comparisons are more complex. Ice melt describes a chemical class of salt that prevent ice from forming. Not every ice melt is made from the same ingredients or used in the same application.

Ice melt won't cause cars to rust, nor will it damage rebar, pavement or concrete. Rock salt diminishes the lifespan of surfaces. This alone may justify switching to ice melt.

Best Ice melt brands and applications:

  • Calcium Chloride products such as Morton Ice Melt Pellets work quickly.
  • Calcium Magnesium acetate such as Melt EB Ice Melter is commonly used by contractors and found to be a safer type of melt.
  • Magnesium Chloride such as Melt Man Ice Melt is best for pet owners, however, it does not last as long as other ice melts and is more expensive.
  • Urea ice melt is considered safer, even though it may still kill grass and plants. However, with the added safety, you lose effectiveness.
  • Crystalline amide, used in Safe Paw ice melt, is one of the only ice melts that guarantees its safety around children and pets. It is time released, effective, and doesn't damage surfaces. However, it is arguably the most expensive ice melting solution.

Characteristics of Rock Salt and Ice Melt

Charachteristics
De-Icing Rock Salt
Anti-Icing Ice Melt
Composition
Sodium Chloride (NaCL), Calcium Magnesium Acetate
Potassium Chloride, Urea, Magnesium Chloride
Chemical Form
Halite
Calcium Chloride
Chemical Reaction
Endothermic (Absorbs Heat)
Exothermic (Releases Heat) Calcium Chloride, Magnesium Chloride, Endothermic: Urea
Environmental Safety
Kills plants when the salt to water ratio is 1:2
May also kill plants, but can be avoided by moderation and removing excess material.
Temperature Performance
Melts ice until 0 degrees F.
Prevents ice from forming until -7 to -25 degrees F
Pet Safety
Not safe for pets.
Some brands are safe for pets. Check label.
Damages metal and sidewalks
Yes
No
Concrete Performance
Corrosive to concrete
Safe for concrete
Pavement Performance
Corrosive to pavement and rebar
Not harmful to pavement or rebar

Getting Prepared

Property owners should always prepare for winter by stocking up on supplies ahead of time. Ice melt needs to be applied before the precipitation, whether that be rain, ice or snow. Rock salt should also be on hand before the bad weather comes in.

After a long warm summer and a cool relaxing fall, the last thing we want to think about is snow and ice storms. Anyone who lives in areas with cold, harsh winters knows that forgetting to buy road ice removal products can be a dangerous mistake.

Things to buy before the first snow of the season:

  • Snow shovel or snow blower
  • Rock salt or ice melt
  • Ice scraper with snow brush
  • Thick gloves
  • Snow roof rake

In many areas, it is not uncommon for stores to run out of road salt and ice melt when a storm is coming. This drives prices up and can cause unneeded stress. The best time to prepare for snow and ice is to plan ahead.

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    © 2017 Melody Trent

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