It's one professional welders experience using brake clean to clean parts before welding because he was out of his normal carb cleaner. It's scary because most people wouldn't even think about it before doing it...
http://www.brewracingframes.com/id75.htm
With that said,cleaning the area with a grinder, sand paper, flap wheel or wire brush is about as much as you need to do for prep work before welding and this story is one reason why you don't use solvents.
I had never thought about this and could easily have done this myself since a case of brake parts cleaner is usually my parts washer.....