Where it really causes damage is when it doesn't get the chance to evaporate quickly, like when it is sprayed into a blind hole. Then it can really start to work on the aluminum and cause corrosion similar to rust. Sometimes the chemical reaction can be dramatic, with foaming stuff coming out of the hole and the threads in the hole pitted and visibly damaged. Sprayed on surfaces it is not that big of a deal but oftentimes machined ports have tapped holes in them.
The reason I wrote the original post was to say when and why I would use them. The non-chlorinated brake cleaners work very well for what they are made for. When I use chlorinated brake cleaners it is not for cleaning brake components. I just use it for cleaning non-aluminum parts when using anaerobic adhesives, like thread locker adhesives, for example Loctite. I feel that the minimal use of these solvents and the dangers they pose is outweighed by the utility of these types of solvents. The types for sale now cause minimal damage to the environment while at the same time help to keep mechanical components from coming apart. It is certainly a judgement call on my part. I think these types of solvents should only be used for fasteners and cylindrical fits and the like when anaerobic adhesives are being used. There are less harmful but also less effective solvents available.
