Looks like it's just as bad as Sodium Cloride to me:
MAGNESIUM CHRLORIDE
Magnesium Chloride and Sodium Chloride are both very corrosive to the metal surfaces of your vehicle. Depending on what type of metals we're talking about, the amount of corrosion and the effects will be different. For instance your body could be steel or various alloys and your wheels could be aluminum, magnesium or a combination. Your wires could be copper and so on. The effects vary on each one and then you have to take into consideration the coatings.
According to a long winded 2 Phase study done by CDOT (Colorado Department of Transportation) the difference in the corrosive effects between the Mag. Chloride and Sod. Chlorides were quite different. After studying their test, it was clear they came up with 2 very different conclusions. To make a long story short, the 2 studies both showed that the two chemicals were very hard on metals of all types. But where each one differed was which was worse. It all came down to the environment they were used in. In the wet stage, the magnesium was more corrosive and in the immersion stage the sodium was. Since both solutions are used on the roads in Colorado you can figure out for yourself that your vehicle is in trouble since the majority of you vehicle is made up of some type of metal.
Mechanics have noticed severe rust build up on the brake shoe table called rust jacking by brake engineers, and it is causing break linings to deform and work boots to crack and break. They are also finding break lines that weren't 50% worn, but were cracked and showed uneven wear.
In press releases and product brochures, these chemical companies promise these chemicals are less harmful to metals that rock salt. Most professional drivers disagree. Seasoned truckers say these chemicals eat away wheels, housings, and gas tanks and are rusting the truck where it pits the paint.
As a professional car care specialist for over 24 years, we saw the beginning of the use of Magnesium Chloride, and we've seen the effects. Not sure at first if our hunch was right, BUT, the past few years proved it was. You may notice little rust looking spots on your expensive rims and chrome or paint chips rusting over night. Mag. Chloride is the cause. It is also thicker than sodium chloride, so it sticks to your cars finish and is next to impossible to wash off. Even by hand!
http://www.aautodetail.com/code/magchloride.html