I've been using Blue Beacon for about 18 years now and the only word I've ever heard them call it is...brightener. I never heard brine but it doesn't matter.
It's a mild acid of sorts but don't know any more than that. I always have them use it on my aluminum wheels and fuel tanks just before I polish them. It cleans them very nice (removes oxidation) and allows for a brilliant shine when I apply the polish. In that process, they spray the "brightener" on very quick and immediately blast it right off with lots of rinse water.
If you allow them to, they use it on the entire truck and/or trailer as a quick convenience as opposed to soap and brush. I actually prefer the acid so that I can avoid possible scratching or swirl marks from brushing. I've never seen an issue even over the course of several years of use on a truck's paint.
The bad thing is that sometimes a newbie will forget to be careful and will get the acid on my polished aluminum wheels and tanks. Sometimes leaving white streaks and others will completely whiten the aluminum. I put a lot of effort into making my truck shine and it's downright frustrating when they mess it up with the acid.