What is the truth about ice melters?

Okay. I spent a couple of hours checking labels and scouring the internet in search of the facts about what ice melters work best, what ones are safe for concrete, and what ones are safe for pets. There is a lot of confusion and a lot of deliberately misleading advertising out there. So I will tell you what I have found out in the short time I devoted to it, and what my personal experience has been.

Types of Ice Melters

Rock Salt ice melter

All ice melting chemicals have one thing in common; they are eutectic or they lower the freezing temperature of water when they dissolve. The most common type is salt. That word “salt” is a tricky word, because in normal conversation it means table salt, rock salt, or solar salt. All these salts are the same chemical; sodium chloride. But in the world of chemistry, there are several other salts, all with similar chemical properties. The salts sold as ice melters are sodium chloride (rock salt), calcium chloride, potassium chloride, and magnesium chloride. These all work the same way, but work at varying temperatures, and impact the environment differently.

There is an ice melter out there called magnesium chloride hexahydrate. Some sources I found group this with the salts. Some said it is a non-salt. Not being a chemist, I don’t know for sure. But it is clearly related to magnesium chloride, which is a salt.

Combotherm ice melter

One non-salt ice melter is Urea. Urea is the second largest component of urine after water, and is also used as a component in fertilizer. The good thing about urea is that it is non-corrosive. Two bad things about it are that it doesn’t work at very low temperatures, and it is a biological hazard if used too much. It reduces oxygen levels in rivers and streams, and can kill fish populations.

Another non-salt ice melter is CMA or calcium magnesium acetate. CMA was developed specifically to be a non-corrosive ice melter. And it works at about the same temperatures as rock salt. The down side is that it is much more expensive than any of the other ice melters; up to 30 times more expensive.

Sugar, like salt, is eutectic; it lowers the freezing point of water. So it can be used as an ice melter. And it is non-corrosive. But the effectiveness of an ice melter is dependent on the number of molecules per gram. And Sugar molecules are big compared to salt molecules, so they don’t melt nearly as much ice.

There are also a lot of ice melters that are blends of some or all of these.

“Safe” for Concrete

Ice B'Gone Magic ice melter

In a nut shell, no ice melters are safe for concrete. And almost every label I read says this. Concrete is porous. So it absorbs water. When an ice melter melts ice, some of the liquid water is absorbed into the concrete. Then, if the temperature drops, that water will freeze. When the water freezes, it expands, and can crack the surface of the concrete. You can’t melt the ice with anything without running the risk of damaging the concrete. That said, the salts tend to be slightly acidic, which causes additional corrosion. So straight salt (sodium chloride, calcium chloride, potassium chloride, or magnesium chloride) will cause more damage than an ice melter that is a blend of salts and non-salts. In fact, sugar, CMA, and/or urea can dramatically reduce the corrosiveness of salt. So if that is your main concern, you should look for a blend.

“Pet Friendlier”

SafeStep SurePaws ice melter

I found a few ice melters that said they were safe for pets. Some don’t list their ingredients, so it is impossible to check their claims of how well they work. The active ingredients in Safe Step SurePaws ice melter are magnesium chloride hexahydrate and potassium sulfate. I also found several ice melters that said they were “Pet Friendlier” which I take to mean that although they are not 100% non-corrosive, they are much less corrosive than straight salt. These were all blends of some kind of salt and a non-salt.

Which Melts Ice Best?

Calcium chloride ice melter

Calcium chloride seems to be the best ice melter, if that is your only concern. It works at the lowest temperature (-25 degrees F) and it melts more ice per pound. It is also generally about double the price of simple rock salt. CMA works at the same temperature as rock salt (15 degrees F) but it is about 30 times more expensive. Urea works down to 10 degrees F. I haven’t found the other salts or sugar outside of a blend.

My Personal Experience

I’ve used rock salt, calcium chloride, Combo-therm (a blend of calcium chloride, potassium chloride, magnesium chloride, and sodium chloride), and Ice B’Gone Magic (rock salt with an agricultural additive that makes it less corrosive). The calcium chloride works great. It starts as soon as you put it down. You can hear the ice crackling as it penetrates the surface. It also doesn’t leave any visible residue if it is tracked into your house, as rock salt can. I had a new concrete walk put in about ten years ago. I’ve used calcium chloride on it every winter since then with no noticeable damage. I don’t know if I am just lucky, or if conditions at my house are unusual.

I hope that answers some questions.

Andy Daly

Sources

https://www.scientificamerican.com/article/why-do-we-put-salt-on-icy/

https://www.rjcenterprises.com/blog/which-ice-melt-makes-most-sense/

https://safestepmelters.com/product/safe-step%C2%AE-mag-chloride-8300%C2%AE