Instruct: Classify Amazon reviews into positive or negative sentiment
Query: This garbage is nothing more than snake oil...

I bought a bottle of this stuff to get some rust out of some tight spots in a heat shield I bought from the junkyard. After cleaning the rust and scale off all the areas I could, I applied a heavy coating of this stuff and worked it in with a brush. Waited 15 minutes, rinsed it off and it did absolutely nothing. Don't waste your money.