I like using the phosphoric acid based products for removing rust. I've used them on large sheet metal parts that I don't want to blast for fear of warpage. I did the roof on my 1937 Buick Buick and with a little work and patience I got the rust out of the deep pitted surface rust.



Over the years I've used Krudkutter brand, a Rustoleum brand phosphoric based product. It was the lowest cost product I could find. I bought it in the spray bottle and also in a gallon jug. I can no longer find it in the gallon jug what was ounce for ounce cheaper then buying it in the spray bottle. My son is a dairy farmer and uses different chemicals to clean his milking equipment and most contain some kind of acid. One product he uses is Milk Stone Remover and Acid Rinse. The main ingredient is phosphoric acid. It has by percentage, about twice the acid content as the phosphoric based rust removal products but cost less than half of the one offered by places like Eastwood. It does have a bite when using so you should take the proper safety precautions you would use when working with acid.




These are two parts from my Buick that were very badly rusted, very deep heavy rust. I left them soak in the acid for a couple of days and with a little work with a wire wheel on my angle grinder they came out very clean with not rust. They are heavily pitted because they were so badly rusted but the deep pits have no rust.

 

Great info Bob!!

I'll try to remember that when I get back to work on the roadster

 

Good info. I have used food grade citric acid, mostly on a couple of Model TT Ford running boards I wanted to use as shelves. Worked great. I also bought a gallon of Rust 911, diluted to directions and cleaned both halves of my 8RT. Water jackets came clean. Was impressed.

 

Never heard of Rust 911. After I saw your post I surfed around a bit to find more information. It sounds like a good product. I'll have to try it.

I've used citric acid to passivate stainless steel. I do a lot of control systems for food machinery. Most won't allow mild steel to be welded or worked on in the same area as stainless because the stainless can pick up contaminants from the steel being welded and cause the stainless steel to develop rust. One place I work at does do both in their shop but they passivate their machinery with acid, some pretty strong stuff but they told me I could use citric acid to do the small jobs I do.

I've read many posts in the past about using muriatic acid to quickly remover rust. I won't allow the stuff in my shop. I used it once to clean copper bars before tinning them. First, the stuff made me choke. Second, after I was done with it the next day every piece of unpainted steel within 10+ feet of my work area had a layer of rust on it. Third, I had the bottle with the remaining acid on the floor of my shop and over time it developed a small leak and ate into my cement floor. I bought about a half dozen boxes of baking soda to neutralize the crap before getting rid of it.

The phosphoric acid products leave a black coating that is supposed to prevent rusting. I'll have to get the Rust 911 and try that.

 

Expensive for a gallon, but diluted to directions, it makes 16 gallons. I left water pumps on, leveled block and filled to top of cylinder deck. I had it in my shop office, and turned up heat til it was around 70. I left it alone for 2-3 days, then drained, flopped block over and poured same stuff in other bank. Was quite pleased to see raw cast iron in water passages. I had already scraped sand/creek mud, etc from bottom of passages.

 

I used to get phosphoric acid in many products in Canada, mostly in steam cleaner coil cleaner, but in the last couple of years it has become unavailable in any form.
I use it as a soaking solution for small parts for overnight or a few days so it doesn't have to be a 100 % concentration.
The only reasonably priced product I have been able to find is a commercial bathroom and tile cleaner that contains some phosphoric, it just takes longer, but works well.

 

https://greggdistributors.ca/automot...asers/llo25904
Have you tried this? Contains phosphoric acid. Doug.

 

I found this. High percentage and not too expensive. Looks like brewers use this to adjust PH.

 

I use a product called OSPHO (also phosphoric acid based) for all my rust / corrosion removal. Works great, I've seen it at other places too, but I primarily buy mine from Ace Hardware locally since we have a ton of locations, and each carries several gallons if I'm doing a larger project. Nasty stuff though, it will etch into concrete a good 1/8" deep if you let it sit for a long period of time, so you need to make sure the stuff you don't watch affected is properly covered with a tarp or cardboard.

We actually have a local garage floor epoxy company that uses this stuff as their concrete etcher before putting epoxy down. Gives the epoxy a good bite on the etched surface.

Skyco OSPHO Rust Remover Surface Prep, 1 gal - Ace Hardware

Jim

 

I looked at different phosphoric based products and compare percentage of acid and the cost. The dairy cleaner had the highest percentage of acid and at a better price and it was locally sourced.

 

Last night I was surfing around Youtube and found a video by Ed China, the tall former host of car show Wheeler Dealers. He has his own Youtube channel. The episode I watched was about dunking his Range Rove chassis, or as he called it "shassey" to remove rust. First he built a dunk tank out of portable swimming pool. He then filled it about a 1/3 full of Evaporust. He used over 500 gallons of Evaporust, current cost of Evaporust on Amazon is about $125 for a five gallon pal, he used over $12,500 of the product, probably more since this show is done in England, plus the cost of the swimming pool. Then after he was done, which turned out pretty impressive, he had to drain and store the used product. I would think he could have gotten the frame professionally dipped for a lot less than $12K and not have to deal with the mess. Just another "reality" TV show that isn't very realistic. It was obvious to me it was a big commercial for Evaporust.

 

Sheesh!!

If I were only born rich instead of good looking......

 

I feel for you brother, me too

 

I'm telling you Bob, if the two of us sexy ol dudes ever got in the same place at the same time the shining young darlings would be swooning left and right. Shoot, the governor would have to issue a special directive that said you and I couldn't be within a mile of each other

 

I don't think I'd go that far