Duda Energy 1 Quart / 950ml 85% Food Grade Phosphoric Acid Rust Remover Clean Etch Metal

85% is a very strong concentration for phosphoric acid. I used it, after brushing away loose scale, on rusty cast-iron, wrough, iron, and steel plant stands that we have all over the place. I let the acid treatment sit for a few hours to a day to dry, follow that with a light rinse and dry again, then touch up (spray) paint. It takes longer in terms of duration, but the effort level is lower than sanding and brushing down to bare metal, priming, and then painting. I suggest diluting this acid at least 50-50 to start. You can adjust up or down from there the higher, the concentration you use, the longer it will take to dry, and it tends to take on a greasy sort of feel if the concentration is really high. High quality.

Worked great as a rust treatment on my vw floor pan. Same thing as the expensive brands marketed for the application.

Works great for all sorts of things food grade acid is good for. I bought it to clean my water softener and it's resin bed. Works amazing. Made my 7 year old resin soften hard well water like it's new again. Good price too

I dilute this to use as a flush for my boat diesel engines and air conditioners on my boat. It saves you a lot of money over buying the pre mixed commercial flushes available. Using phosphoric acid versus things like muriatic acid dissolves the particles., mollusks and helps keep your cooling passages clean. My boat is in a saltwater environment. So I have to flush those air conditioners every two to three months during the summer time or I start getting high pressure alerts on the air conditioners. For another tip, add a small copper fitting snd bromine tablets into the strainers to your engines and air conditioners to help reduce mollusk and algae growth.

Most chemical derusters use phosphoric acid to some degree. The commerical products I've used nowadays are seriously lacking in how much of this acid is in their products. For this reason I purchased a gallon of this food grade acid. It's 85% and needs to be handled with caution. I mix it up at a ratio of about 10-15%. Spray it on with a trigger sprayer and let it sit for 5 minutes. You can use a stainless steel toothbrush with it. I spray the brush down with it too. If it's really rusty you might have to do a second application. Make sure you use gloves and face and eye protection. If you have no common sense and are accident prone then don't both with this. I don't take any responsibility for your use or the brewing of this system. If you want a home brewed deruster then this works well. Or you can use the commerically available stuff that's about as effective as KoolAide on your project.

Work ass intended

I wanted food grade phosphoric acid for homebrewing non-alcoholic beers, which require a pH adjustment to get below the food safe range of 4.6. I've lost some batches to infection in the past because I've not acidified my wort. Approximately 3mL of this 85% phosphoric acid solution drops the pH of a 5 gallon batch of wort from around 5 into the low 4's. Due to the small amount used, no perceptible flavor is imparted. It came packaged well and tested at the proper pH (0.5). Obviously, this is a product for people who understand safe handling procedures of strong acids.

You put copper in a 20% solution and it turns bright, shiny, and smoousth. Better than it was, new. I've used it on iron rust too as preparation for repainting an old rusty outdoor chair. The rust was too thick to make the steel shiny, but it served the purpose. I'm sure it would work with many other metals. Prior to the invention of carbonation for soda, around 1920's they'd put a tiny drop of it in a soft drink. Its nice enough, though you can see why carbonation has replaced it. It is a real acid so treat it like one! You should dilute this stuff before using. OTOH, if you get some on your skin, you have time to run to the sink and wash it off before you get burned. Safer than, say, nitric acid. And strong acid is fun to try for all sorts of uses in the garage! Do not use w/o adult supervision.