Winter, salt, corrosion and CortecAnna Lee
Most sections of the country had significant (record breaking) snowfall in 2015. One consequence of heavy snow fall is lots of snowplowing and road salting. Salt does a great job in “melting” ice, but it also accelerates metal corrosion.
Two misconceptions about salt is one- it actually melts ice and two it corrodes metal. A better statement would be that salt contributes to, or accelerates these phenomena.
- First, why is salt used to melt ice? The definition of melt is: “make or become liquefied by heat”. In spreading salt on ice, there is no rising of temperatures. Many mistakenly believe that there is a chemical reaction between salt and water that produces heat. What really happens is that salt combines with water (ice) and lowers the freezing point. When water freezes, the molecules form solid crystal structures that prevent molecular movement. Salt breaks down into sodium and chloride ions that interweave with the water molecules and prevent the crystallization. Adding salt to water can reduce the melting point from 32 degrees F to around 16 degrees F.
- Second, why is salt associated with corrosion or rust? Some mistakenly believe that salt “eats” away at metals like an acid. This isn’t exactly what happens. First what causes rust? Rust occurs when iron gives up its free floating ions to oxygen and form a new substance called metal oxide. In order for this transfer to occur, there needs to be a medium for the iron ions to transfer to the oxygen ions. Water is the typical vehicle. But pure water has very few free ions to facilitate this process. Salt readily combines with moisture and attracts moisture, while also contributing free ions. This accelerates the process of metal giving up its ions to oxygen, thus salt accelerates the corrosion process.
Salt is not only prevalent as a deicer for roads, but it is also in our oceans and the salty mist that is above the ocean. Automobiles that drive around in cold climates or on the coast will get subjected to salt which will accelerate corrosion. Also metal products that get shipped overseas will also get exposed to salt mist and may experience corrosion because of this.
How do you prevent corrosion? Prevention may be a strong word, because regardless of treatment or coating, every metal will corrode. It may take 100’s of years, but it will corrode. So the better, more accurate term is inhibiting corrosion. The way to inhibit corrosion is to retard the ionic transfer process described above. If one can prevent the metal from giving up its ions, then one can slow the corrosion process. There are a number of ways you can try to inhibit corrosion; preventing moisture from contacting the metal surface, coating or plating a non-corrosion metal such as zinc are a couple of methods, but they may not be practical. Cortec’s sells a variety of corrosion inhibiting products that are practical, don’t change the properties of the metal and are environmentally friendly. Cortec’s VpCI product essentially emits a cloud of ions that bond to the metal surface and prevents the metal from giving up its ions, essentially locking them in place. These coatings can work as a short term solution for products shipping overseas or be used as a longer term solution such as automotive applications. Cortec has provided solutions for thousands of applications from storage of equipment to concrete reinforcements to delicate electronics.
Packnet is a distributor of Cortec’s products and routinely uses them in its custom packaging and crating solutions. Corrosion prevention is an important part of our mobile crating and packaging service. If you have a potential corrosion issue, then you may wish to contact Packet at (952) 944-9124 or you can visit our corrosion inhibiting section of our website.