In the public garage where my wife parks while at work, we’ve gotten some streaks of what looks like salt but doesn’t want to come off the paint. I imagine it’s some sort of ice melter, but I don’t want to rub it too hard and damage the paint. Any suggestions?
If it does not come off with warm water and a soft cloth it is not salt! It could be lime plaster or cement streaked on the car by careless construction workers. I would try to get that off with a scratch removing compound while gently rubbing. Please check out other compounds at auto supply stores, or phone a car detailing shop; they will know exactly what to use.
Whether it’s ice melter (calcium chloride) or a lime product (calcium carbonate) it can easily be dissolved by an acid solution such as household vinegar.
Is it a multi level garage? Almost anything can leak down from one floor to the next including dissolved building materials. You may want to contact the garage management. I once got a free paint job when I was spattered with concrete from a construction site I drove past.
If that is not an option you choose, then consider an auto detailer. They tend to be able to handle many of those problems.
Trying vinegar is an excellent idea. follow it immediately with a good bit of water to wash it off. Do not use an acid stronger than vinegar; it might damage the car and you.