Hi there, I’m a newbie here, hoping someone might be able to help. We purchased a slk250 2014 secondhand 18 months ago. It’s our retirement treat and husbands pride and joy.In great condition from a private dealer, we wanted to keep it that way, so they advised us to have a Williams ceramic coating put on which they did before we collected it. We were very impressed with the independent high end dealer, and have no reason to mistrust them. However we now have micro blisters appearing all over. We’ve sent them photos (they are couple hundred miles away) and they have suggested we take it to Mercedes as it will be covered by anti corrosion guarantees. We haven’t done any more yet, but wondered if the guarantee will be negated by the coating? Any help please, forewarned is forearmed!