Cold icy weather creates major safety problems on paved surfaces for a large part of the world during the winter season. Salt is by far the most popular material used around the world for melting ice. Because of the proliferation of choices, buyers are becoming more and more confused as to which salt to buy. This article answers the frequently asked questions (FAQ) from buyers regarding the usage of salt to melt ice. These FAQ were accumulated over many years by a minority operated woman owned janitorial supply company.
1) Is salt another name for rock salt? ANS: Yes. The term salt is commonly used referring to table salt, sea salt or rock salt (Halite). However, any chemical compound formed by neutralizing a base and an acid is technically a salt. Salt compounds are held together by ionic forces between two or more elements. It is the ionic properties of the salt compounds that allow them to melt ice. The chemical compound for table salt, sea salt and rock salt is Sodium Chloride (NaCl).
2) Will salt kill my vegetation? ANS: Yes, but only in very high concentration. Care must be taken to minimize the build-up of salt around vegetation. Any damage to the soil is usually temporary since normal precipitation quickly dilutes the salt.
3) Should I use a non-salt product? ANS: No, without metal corrosion is a major concern. Salts have been overly criticized for their effect on the environment. The fact is that salts dilute quickly during spring rain and snow melt minimizing the potential damage to vegetation and animals. Most non-salt products contain urea, glycols or fertilizers that are much more damaging to an ecosystem because these products cause fish kill.
4) What are my salt choices? ANS: The two basic choices include: 1) inorganic salts such as Sodium Chloride (NaCl), Potassium Chloride (KCl), Magnesium Chloride (MgCl2), and Calcium Chloride (CaCL2), or 2) organic salts such as Sodium Acetate ), Potassium Acetate (KAC), and Calcium Magnesium Acetate (CMA).
5) Are inorganic salts safe? ANS: Yes, but only when the salt is used as instructed. Inorganic salts are more corrosive to metal. Some of the more aggressive inorganic salts can burn skin and pet paws. "Concrete corrosion" from the usage of inorganic salts is not really a corrosion process. "Concrete corrosion" is a progressive cracking process caused by the brine freeze / thaw cycle as temperatures move above and below the freezing point. The inorganic salts are less expensive and therefore more frequently used by the majority of buyers. When the package instructions are followed (using gloves, keeping away from unprotected metal, avoiding fresh concrete, following application rates, etc.), the inorganic salts are very safe.
6) Is chloride inorganic salt safe? ANS: Yes. The chloride ion present inorganic salts comes from the element chlorine which is one of the most abundant elements found on the planet. The oceans contain the largest amount of chlorine in the form of sodium chloride. Chlorine is used to disinfect the water in rivers, water treatment plants and swimming pools. As with many natural elements, chlorine in very high concentrations can be dangerous.
7) Are organic salts safe? ANS: Yes. Organic salts decay naturally in the environment while having minimal effect on the fish kill issue caused by non-salt products. CMA is no more corrosive to metal than water and will not burn skin or pet paws. Since acetate products are much more expensive than the inorganic salts, usage of acetate products is very limited. Salt granules are often coated with acetates to provide more corrosion resistance around metals. Acetate coatings can also speed up the melting process.
8) Will rock salt work for me? ANS: Probably not. It lacks the performance of other salts and is not effective below +20 degrees F. It melts slower. It allows the freeze / thaw cycle to occur at +20 degrees F. Most customers do not like the white residue left behind when rock salt brine dries up. To work well, it requires lots of traffic to produce heat from friction. Improved corrosion protection on automobiles and bridges has made rock salt acceptable on road surfaces in areas where temperatures do not get extremely low.
9) Is calcium chloride the strongest salt? ANS: Yes. It does the best job melting ice but has some disadvantages. Calcium chloride like rock salt will leave a white residue on carpet when tracked inside. It is the most aggressive salt when it comes in contact with skin or pet paws. Most significantly, it is the most expensive of the inorganic salts. If an application does not require the extreme low temperature (-25 degree F) melting power, it may not be the most cost affective solution.
10) Is magnesium chloride a pet friendly salt? ANS: Yes, most people find that magnesium chloride works best around their pets while still providing good sub-zero melting power (-13 degrees F). Magnesium chloride granules contain 50% water which reduces the tendency to stick to pet paws and dilutes the salt to reduce burning. Even if ingested by a pet, the diluted granules would be less harmful to the pet.
11) Is potassium chloride a salt and a fertilizer? ANS: Yes. Potassium chloride promotes root growth making it a good fertilizer. This does not mean that it is the safest salt for the environment. As explained previously, fertilizers when heavily used as an ice melter can cause fish kill, which is a very serious problem for the ecosystem.
12) How do I choose the best salt? ANS: Often a mix (referred to as an ice melt blend) is the best choice. Manufactures have now developed processes to both blend and coat salt granules to get optimum results depending on the application. The buyer should be aware that it is not the marketing language or fancy packaging that makes ice melt blends better. It is the ingredients.
13) How do I determine the salts used in an ice melt blend? ANS: The Material Safety Data Sheets (MSDS) will provide a list of ingredients. However, the MSDS often does not give the formulation (percentage of each ingredient). Manufactures consider the formulation proprietary.
14) How do I determine the percentage of each salt in an ice melt blend? ANS: One way would be to take a sample to a laboratory for a chemical analysis. This is generally done for very large commercial contracts where the contract specifies the percentage of each ingredient required by contract. Often comparing the price of a product to the ingredients that are listed on the package will allow for a good "guess-timate". Less expensive products always contain greater proportions of less expensive ingredients and smaller proportions of more expensive ingredients.
15) What is the difference between Eutectic Temperature (ET) and Minimum Effective Temperature (MET) of a salt? ANS: ET is the laboratory measured melting point for the salt compound. For salts to work for melting ice, they must go into brine (salt saturated solution). The MET is the temperature of the brine at which freezing first occurs. A buyer should be cautious because some ice melting products will list ET as the minimum melting temperature.
16) What determines the MET for a mix of salts? ANS: Each salt has its own MET. Because there is very little interaction among the basic inorganic salts, the MET is only raised or lowered depending on the proportions of each salt used in the mix. Example: When it is concluded that the percentage of CaCl in an ice melt blend is only a trace level, no improvement in MET is to be expected from the CaCl.
17) How does MET affect my buying decision? ANS: MET is directly proportional in most cases to the price of a product. Paying for a product that will provide subzero protection for an application where the thermometer rarely drops into the teens is not very cost affective.
18) Where can I buy CMA? ANS: The question should be "Why should I buy a CMA?" Pure CMA is 30 times more expensive than rock salt and has the same MET as rock salt. There are very few applications for such an expensive product. Airports are probably the only exceptions because of the need to avoid metal corrosion at all cost. Very few distributors sell 100% CMA. Buyers need to understand that inexpensive CMA products typically include a less expensive salt or urea that has been covered with CMA.
19) Is urea a salt? ANS: No. Urea is a natural product high in nitrogen that comes primarily from the urine of mammals. In an effort to market earth friendly products, many ice melt blends contain significant proportions of urea mixed with salts, fertilizers, etc. Caution must be taken in using urea products because of the fish kill issue. Various forms of traction materials (sand, cinders, calcianated clay, etc.) are often added to urea because urea brine is very slippery.
20) Can salt damage asphalt surfaces? ANS: Yes. The potential for damage exists but is not very likely. Asphalt is a more compliant material than concrete. The free / thaw cycle that causes concrete to scale does not occur on asphalt. However, when the salt brine works its way into asphalt cracks and freezes, the ice expansion can cause crack propagation on older asphalt that is less compliant.