i used hf acid to clean the rails on my trailer and it left black streaks on the alluminum....could it be the type of aluminum alloy???Aluminum will oxidize. Not like steel though, that forms the red orange rust (iron oxide) that will eventually eat through thin steel. When aluminum oxidizes, it leaves a thin cloudy film on the surface. That\'s why nice new shiny diamond plate gets dull after being exposed for some time. It can be removed by some chemicals, apparently your hf acid. When the acid breaks down the cloudy oxidize layer, it may turn into a black residue. You\'ll be left with a clean aluminum surface that will, over time, oxidize and get that cloudy film again. It could also be waste compound of your hf acid etching the surface. Check to see whether the acid you\'re using will etch or clean an aluminum surface.Acid is a slow burn on some metals, aluminum tends to turn black when burned where iron turns red when it rusts or burns. I\'d say the hf acid left some slight burn marks on your rails.I have a charcoal grill with diamond plate alluminum . how can i get it to shine again? I used my steam mop and rag it got most but not all?Other related question