Not to get too geeky here on chemistry stuff, but the way PA works is to form a mostly iron phosphate barrier on the workpiece surface. From a welding point of view that's a dirty surface that needs to be cleaned just like any other "contaminate" prior to expecting a quality weld.
thank you all for the info and sharing of experiences. I am starting to tackle this and its my first attempt at paint and rust nuetralization and this will be very useful
Just wanted to correct these and add a couple of other names to the list. I've done a lot of research into this, getting the data from the companies and MSDS's. Prices might vary, but this is what's in the products. Prices are per gallon retail. Shipping is usually going to add a big hazmat fee. $13, 20-46% in Home Depot Eagle Etch & Clean (strange range on the % there but that averages 33%) $13, 35-40% in Krud Kutter Clean & Etch. $25, 40% in PH-OSPHO-RIC PLUS. $25, 36-40% in Ospho. $40 , 36% in Miracle Sealants Phosphoric Acid Cleaner $160+ , 40% in Picklex Some others like Evaporust don't use acid at all, but the rest are the same. 35-40% H3PO4 and the rest is water, with a splash of surfactants which are water wetters. Same active ingredients, same strengths, same benefits and drawbacks like with the welding. Buy Ospho if you want, but I'll stick to the cheaper ones, plus they're easier to find. I hate to bash or any of them, but at $160 vs $13... I'm sorry, but Picklex is just a scam. Oh, and I would recommend you never, ever use HCl / "muriatic" acid or anything with chlorine in it on metal unless you want it to rust into dust, literally! Don't ask how I know Same thing. Baking soda is sodium bicarb and it should work. Thanks for listening, and good luck to you all fighting this enemy that never sleeps.
Ospho isn't just acid.....it leaves that white powdery coating that prevents new rust from forming. If you use the miracle grow you would probably have to dry and prime it right away.
Bought a gallon of Ospho for about 25 clams at the local Ace hardware. Going to use it to treat the sheet metal on the COE after I remove as much rust as possible first (wire wheel, strip disc etc). I did just use it on the rusty rear brake drums just for a test on the COE. Getting 5 spoke wheels so the drums will show. Just used a wire wheel on a fast air-drill-motor quick to get in between the cooling fins. Ospho treated it overnight - a little goes a long way, then sprayed 4 or 5 coats of mat black 500 degree engine paint spray bomb. For something I didn't care that much about, really looks good. We will see how it holds up on brake drums. I used the Dupli-kote brand I had on hand, but there are others that might be a better choice like Rust-Oleum.
I don't know why some of you have problems welding after treatment, but I actually love how much easier and smoother the welds are after Picklex or De-Ruster by Purple Power. I'm assuming we are talking about MIG welding,not TIG.
I go to Tractor Supply and buy their "Milkstone Remover"...used to wash the calcium deposits off of the inside of milk storage tanks. I've been using it for decades to remove rust. 75% Phosphoric acid...$13/gal.
ABSOLUTELY! On occasion I see folks on here recommending the use of muriatic acid on rust. Don't do it. It may initially remove the rust but will cause even more rust down the line. Even the vapors cause ferrous metals to seriously rust. In my opinion, Phos acid is the way to go to remove rust, but you will have to clean the metal before welding or painting.
After testing some Muriatic Acid on a rust test panel I was shocked and awwed by the result. If I can get a hold of a camera I'll post some picture. It coverted in less that 3 minutes. Maybe I'm being a little impatient but, I dabbed a bit over my T cowl and its taking much longer with mediocre results. I think it has to do with the volume of acid i used
I've read this thread from the begining to end. I've read wash it off, just wipe it dry, let it dry overnight. What is the correct way to use the PA?
You will get all kinds of answers. But I use it in restoration work all the time. It is a staple in my business. I have and will always, wipe it off before it dries. I do not add water to the equation afterwards. If you read mine, I'm sure I said I personally spoke with a DuPont Engineer and we discussed this. I wipe it off. . nuff said?
okay, after following all of this for sometime, i decided to do my own test. i was wondering if i could remove the rust and not the paint on some trim. here are the pictures of a ~48 hour soak in straight white vinegar. i still may use it sometime but only to strip to bare metal. i was impressed at eventually even the really hard rust came off. i washed it off in warm soapy water and rinsed it in hot then dried it off My next step is to keep it sealed up in a zip-lock baggie to see if the rust all comes back.
Answers to how long to leave the acid on depends on what you are treating. If I am working with sheetmetal/body panels I keep the area wet as long as it takes to remove the rust. It may be 15 seconds, a minute, whatever. The key is, don't let it dry. If it dries, then re-wet with acid. Now while this second are ticking away I'm physically working it as well. Usually with a scuff pad. Then when it looks good, white paper towels to take it all off. If I am trying to treat hardware or bracketry or such, I may leave it in the acid over night, or even a couple days depending what I'm looking for on that piece. I may even let it dry, but this is something I will not be painting or giving another finish. If it gets painted, don't let the acid dry on the part without you doing something to prepare it for paint. But DO NOT wash it with water and sit it aside.
"If it gets painted, don't let the acid dry on the part without you doing something to prepare it for paint. But DO NOT wash it with water and sit it aside." Thanks Pete, like i said, mine was just an experiment. Part of it will be to see what happens, as you can see i used a scrap piece, so nothing lost. i was planning on the Molasses next on a similar scrap item.
hope i didn't miss this already being covered.. but... Any concerns with pouring in a gal or two in a "gas" tank that is out of the car and slosh around for a while then pouring out.. let dry for a couple days then use a pour in liquid tank liner / sealant ..?
I have a very rusty old Harley tank. I left the acid in 3 or 4 days, moving the tank position. I then poured it out and let it dry. Then I poured in Master Series silver, turning the tank until it was everywhere inside and poured out the excess. That's all you need to do.
The Jalopy Journal
