Using a salt brine mixture of 80 percent sodium chloride and 20 percent magnesium chloride is particularly effective for very cold winter conditions due to the complementary properties of these two salts.
Sodium chloride, commonly known as rock salt, is widely used for de-icing because it is affordable and readily available. However, its effectiveness decreases significantly at temperatures below 15°F (-9°C) because it is endothermic, meaning it absorbs heat from its surroundings to melt ice.
This can be a limitation in extremely cold conditions.
On the other hand, magnesium chloride is exothermic, which means it releases heat as it dissolves, making it effective at much lower temperatures. It can continue to melt ice even at temperatures well below zero.
Additionally, magnesium chloride is hygroscopic, meaning it can absorb moisture from the air, which helps it to form a brine quickly and start melting ice immediately.
By combining these two salts, the salt brine mixture benefits from the cost-effectiveness and availability of sodium chloride while enhancing its performance in very cold conditions with the heat-releasing properties of magnesium chloride. This combination allows for more efficient and faster ice melting, even in extremely low temperatures, making it a practical solution for winter road maintenance.