I have a little salt in my tank, they seem to be doing fine.. I've read others that said they are okay in a little salt as well. Just be careful not to over do it.
water changes every other day along with gravel vacuuming, temperatures as high as your fish can stand (86 is optimal- not sure if corys can handle that) and aquarium salt is ideal.... but since corys dont have scales, go with half of what the recommended dosage of aquarium salt for most fish is.
Its all here, but I thought I should add that half measures for ich will generally cause you nothing but frustration and eventually dead fish. Please don't light dose the salt, short dose the salt, or anything else that will leave your tank with live ich in it. Cories will be fine at 1-3 teaspoons per gallon, but please read the article as well, it really will be worth your time.
Dave