ACID TREATING - Crust/Rust to Primer

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raygreenwood
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Re: ACID TREATING - Crust/Rust to Primer

Post by raygreenwood » Sat Oct 01, 2011 2:59 pm

Bear in mind....phosphoric acid will only neutralize .001" to .002" deep. With crusty rust like that....muriatic will NOt neutralize it...it will disolve it...so do not be surprised if you have les metal left than you thought. But thats actually a good thing...because then you can let it flash rust and treat it with phosphoroc acid then paint ot. Ray

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davebuckholts
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Re: ACID TREATING - Crust/Rust to Primer

Post by davebuckholts » Mon Oct 10, 2011 2:45 pm

Here's what the rust looks like on the inside of the tunnel...

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How long to let the 30% muratic work before starting to rinse it with water?

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raygreenwood
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Re: ACID TREATING - Crust/Rust to Primer

Post by raygreenwood » Mon Nov 07, 2011 5:31 pm

Sorry for the delay. Test a small spot first so you can get an idea. It fizzes when itsworking. It stops fizzing when the acid is neutralized. Keep rebrusing the small spot with acid unit the rust is seen to be gone and the acid stops fizzing. This will give you an idea of how long and how much acid.

By the way its better to put the acid on in successive treatments instead of just dumping it all in there. It will smoke a bit and too much acid is just a lot of dangerous liquid to control. Ray

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Re: ACID TREATING - Crust/Rust to Primer

Post by hugging corners » Wed Feb 22, 2012 10:43 am

Most recently i have experimented with electrolysis, muriatic and phosphoric acid for cleaning gas tanks. Did 3 tanks with it. This are my reactions:

Use electrolysis to clean up the gunk. It also loosens up old paint and makes it more potent for the effect of acid.
Use muriatic acid as directed in the tread
After muriatic acid is neutralized with water, tank dries up and develops surface rust treat it with home depo' surface cleaner (phosphoric acid)
.....I have used "rustolen'um" rust reformer, and Nap'as "Naval Jell'y"- sources of phosphoric. THEY DID NOT WORK in the tank application. Those products are only good if brushed into the surface, aslo they leave white residue. But in tanks you cannot access inside space, and it was a waste of time and 20 dollars.
After all It worked well, when I poured generic phosphoric masonry cleaner from paint dept of the store!

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supaninja
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Re: ACID TREATING - Crust/Rust to Primer

Post by supaninja » Wed Feb 22, 2012 11:00 am

Muriatic acid is fun when you need to remove aluminum



As far a phosphoric acid goes, I really like POR's metal ready, just spray it on the surface rust, and watch it change colors. It doesn't leave crap all over the metal that is hard to clean off either.
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hugging corners
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Re: ACID TREATING - Crust/Rust to Primer

Post by hugging corners » Wed Feb 22, 2012 12:19 pm

por15 metal ready- i wish i could get it locally when needed. For the price it looks good!!
Masonry phosphoric cleaner still leaves soapy residue and it is dilluted form of acid (but cheap as well- 12 bucks a gallon)

Chris4747
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Re: ACID TREATING - Crust/Rust to Primer

Post by Chris4747 » Sun Apr 15, 2012 4:42 pm

no ive been doing metal fab work for 20 years and have used a lot of ozpho.its best if you can take a wire wheel on a drill or grinder and clean the area be for you prime it but its not nesasary . i would use some acetone or denature alcohal to clean the surfases even the oil from finger prints can mess up a good paint job just remember once you use an oil base paint thats what you have to stick to unless you stripp it completely back to bare metal ospho and a good primer should do for a good long time
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Daniel G
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Re: ACID TREATING - Crust/Rust to Primer

Post by Daniel G » Fri May 04, 2012 3:48 am

I just wanted to add some new information I learned to the thread. As awesome as Ospho and other phosphoric acid treatments are, be cautious about using them if you are planning on coating over them with epoxy or other automotive paints. Some primers will fail if used over an acid treatment. So check with the paint manufacturer before using Ospho. Otherwise you may end up having to repaint the car again down the road.

In my opinion if you scrubbed the metal with phosphoric acid to dissolve surface rust, but then rinsed all traces of the acid off, you would probably be fine to epoxy over it. I think the problem is letting the Ospho dry on the metal and then using epoxy primer over it. But I have no experience with this, so don't test it and then blame me later down the road. If you are using something like Masterseries or POR-15 you would be fine as both of those products recommend or include a phosphoric acid treatment in the prep.

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Re: ACID TREATING - Crust/Rust to Primer

Post by hugging corners » Thu Sep 27, 2012 3:05 pm

bump: bouble take from my buildtread, yet very appropriate here!
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Spheromike
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Re: ACID TREATING - Crust/Rust to Primer

Post by Spheromike » Sun Aug 24, 2014 12:53 am

I cant wait to use this on my bug i have some cleaning to do

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Piledriver
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Re: ACID TREATING - Crust/Rust to Primer

Post by Piledriver » Sun Aug 24, 2014 1:32 am

Daniel G wrote:I just wanted to add some new information I learned to the thread. As awesome as Ospho and other phosphoric acid treatments are, be cautious about using them if you are planning on coating over them with epoxy or other automotive paints. Some primers will fail if used over an acid treatment. So check with the paint manufacturer before using Ospho. Otherwise you may end up having to repaint the car again down the road.

In my opinion if you scrubbed the metal with phosphoric acid to dissolve surface rust, but then rinsed all traces of the acid off, you would probably be fine to epoxy over it. I think the problem is letting the Ospho dry on the metal and then using epoxy primer over it. But I have no experience with this, so don't test it and then blame me later down the road. If you are using something like Masterseries or POR-15 you would be fine as both of those products recommend or include a phosphoric acid treatment in the prep.

The issue is OSPHO and many related rust treatments are not just phosphoric---they leave a thin protective coating.
It is not ~pure phosphoric acid as "metal prep" is... likely its the coating causing bonding issues. Seen it myself.
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Prtexx
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Re: ACID TREATING - Crust/Rust to Primer

Post by Prtexx » Sun Aug 24, 2014 9:59 am

I have used electrolysis for striping set up a 300 gallon tank. Experimented with different solution it works fairly well by is only good for line of site and won't clean between layers or inside cavities. Phosphoric acid works great for surface rust with a little heavier rust use a scotchbrite pad. I use straight acid from Home Depot $15 a gallon it's called prep etch you and it can be diluted 4 parts water to 1 part acid for wiping light surface rust (fingerprints,flash). For really heavy rust, I have a tank with molasses (1 part molasses to 9 parts water) just throw the parts in for a week or 2 and the come out totally rust free. Rinse with a hose let the dry in the sun and wipe with the phosforic acid sutio.
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