Magnesium sulfate and frame damage
 

Our town in Connecticut has moved away from sand and salt in the snow and ice battle to rock salt coated with magnesium sulfate. They spray this stuff before the snow actually falls and supposedly snow melts on contact. Cheaper, biodegradeable and more effective than sand and salt mix. Down side is I heard it is more corrosive to cars and I'm assuming bikes. I'm trying to commute as often as I can on my steel LHT and I wondering what this stuff is doing to my frame. I applied Weigle's rustproofing when I built my bike so I hope I have some protection but you never know. Does anyone re-apply rust proofing before a winter of commuting?

Probably magnesium chloride not magnesium sulfate (more ions). Any chloride salt is corrosive but it's easily removed with water. Mag chloride is somewhat less soluble in water than sodium chloride and a little more hygroscopic (water absorbing) than regular salt. That's it's problem with being more corrosive. It holds onto the metal and absorbs water from the air so it has more chance to remove metal.

Rinse the bike after a sloppy ride and at the end of the snow season, go over it very well to remove all of the salt (mag chloride, like sodium chloride, is a salt). You really shouldn't have any issues.