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Old 07-28-2017, 09:14 AM   #1
qmdv
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Default Mouse piss rust

About 6 years ago I bought a reproduction 1932 Ford Roadster metal body. After 3 years in my shop I noticed small round (irregular borders) spots of rust mostly on horizontal surfaces. And no I had not primed the body yet. So I orbital sanded with 180 grit to the point that there was not visible rust. Then primed with epoxy primer (DP 50 LF).

Now I am prepping for paint. I noticed lots of rough white round stains on top of the primer. Also there is rust coming up through the primer from the original rust from 4 years ago. After sanding the primer I see that it protected the metal from the white stains on its surface. I have sanded off all the primer and the original rust spots. You really have to look close to see where the rust was.

I am convinced that the culprit in this saga are field mice.

So now I want to prime and paint but am afraid that this stubborn mouse piss rust will eventually work its way back to the surface.

Should I use a wire wheel on a hand grinder? Is there a rust inhibitor that will stop this mouse piss rust in its tracks. I bought some POR 15 Rust Preventive but in reading about it it says that it seals the area to stop oxygen from getting in. Not sure if that is enough.

Tim
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Old 07-28-2017, 09:22 AM   #2
Seth Swoboda
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Default Re: Mouse piss rust

I would think that if you sanded the body or area of rust, then wiped it down with a wax remover/degreaser, primed, sealed and painted it would be fine. Some of the expert paint and body guys here will chime in.
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Old 07-28-2017, 09:54 AM   #3
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Default Re: Mouse piss rust

Sandblast the area
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Old 07-28-2017, 10:08 AM   #4
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Default Re: Mouse piss rust

When removing rust or a rust stain the dark spot or dis colored spot needs to be gone where the rust was. Once that is achieved I would put on an epoxy primer such as ppg DP90 or whichever products you use. Let it dry for 24-48 hrs. then scotch-brite,prime and paint.
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Old 07-28-2017, 10:16 AM   #5
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Default Re: Mouse piss rust

Urea is a close relative of ammonium nitrate except for a carbon atom in the mix. This stuff is pretty much neutral PH while it's still wet (ammonia and slightly salty water) but let it dry and it becomes a sponge for all sorts of oxidizing ions. It will attack the paint and the steel just like straight salty sea water. It can be neutralized by chemical treatment but it generally does a lot of damage before it's noticed. I suggest a mild phosphoric acid treatment like ospho prior to cleaning for paint. At least this way any iron oxides on the surface of the metal would be converted to iron phosphate. You can even wash and sand the surface after the treatment but at least the existing corrosive stuff is converted.

Urine can be as bad a sea water for corrosive effects unless it is flushed off with fresh water while it is still wet. That doesn't help bare steel though. It has to have a good barrier coating on it.

Last edited by rotorwrench; 07-29-2017 at 06:11 AM.
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Old 07-28-2017, 10:41 AM   #6
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Default Re: Mouse piss rust

If you bought a body and/or any bare sheet metal, leaving it sit unprotected over an extended period of time was an invitation for trouble.
There are several "rust transformers", metal prep's, on the market which you should have sprayed on the bare metal to protect it.
Do not grind and/or sandblast the metal to get rid of the "stuff" that is on the metal, take it to a stripper, have the body dipped to remove the primer, etc., that you have applied to the body. After the body has been chemically stripped have it dipped into a neutralizing solution, which most of the strip shops offer. The metal will be a light grey in color after it it neutralized, it can sit for years in this condition with no rust and/or other issues occurring.
My 39 conv sat in an open field in Montana for 38 years prior to me finding it in 1996. I had the body dipped to remove the paint and rust. It came out of the tank as "white metal" with some panels looking like cheese cloth.
The company that dipped the body did not offer a metal prep/neutralizer as part of their service. I went to the paint store, purchased "JASCO PREP & PRIME" surface prep. which is basically phosphoric acid with some other additives.
I sprayed the bare metal using a hand pump spray bottle and put the car into a container for two years.
I would advise against the use of any of the Old School brews like vinegar, muratic acid, etc.
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Old 07-28-2017, 01:10 PM   #7
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Default Re: Mouse piss rust

You need a cat....
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Old 07-28-2017, 01:28 PM   #8
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Default Re: Mouse piss rust

Cats, dogs, or whatever other mammal that likes to pee on things are all about the same. I still need to repaint the bottom of my tool box due to some cats I had in the hangar a few years back.
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Old 07-28-2017, 03:09 PM   #9
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Default Re: Mouse piss rust

Bare metal needs to be etched with an acid before any sealers or primers. What Roto said is correct. Microscopic rust is forming there immediately after sanding to bare metal or sandblasting due to the O2 in the air. The acid converts the iron oxide to an iron sulfate that stops the process. Othewise, you will see it again later.
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Old 07-28-2017, 06:08 PM   #10
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Default Re: Mouse piss rust

Anybody use this. https://www.semproducts.com/manage/h..._rust-mort.pdf

Tim
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Old 07-28-2017, 09:26 PM   #11
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Default Re: Mouse piss rust

Just basically Phosphoric acid.
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Old 07-28-2017, 10:23 PM   #12
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Default Re: Mouse piss rust

Quote:
Originally Posted by rotorwrench View Post
Urea is a close relative of ammonium nitrate except for a carbon atom in the mix. This stuff is pretty much neutral PH while it's still wet (ammonia and slightly salty water) but let it dry and it becomes a sponge for all sorts of oxidizing ions. It will attack the paint and the steel just like straight salty sea water. It can be neutralized by chemical treatment but it generally does a lot of damage before it's noticed. I suggest a mild phosphoric acid treatment like ospho prior to cleaning for paint. At least this way any iron oxides on the surface of the metal would be converted to iron phosphate. You can even wash and sand the surface after the treatment but at least the existing corrosive stuff is converted.

Urine can as bad a sea water for corrosive effects unless it is flushed off with fresh water while it is still wet. That doesn't help bare steel though. It has to have a good barrier coating on it.
Nice to know we have a mouse piss expert on board. LOL
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Old 07-29-2017, 06:16 AM   #13
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Default Re: Mouse piss rust

I think about everyone that has ever started working on an old car or truck has gotten into at least one old vehicle that's had a nest of stinky varmints living in there. Those who have know the smell too well. I don't think I'd consider myself an expert but I'd agree to being "experienced".

You would be surprised of all the critters I've found living in old airplanes and helicopters too.
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Old 07-29-2017, 10:27 AM   #14
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Default Re: Mouse piss rust

I don't claim to be an expert, and/or an experienced auto painter, however, I did want to be one when I was in my late teens. I worked in a couple of body shops doing metal work and prepping cars for paint.
As my interest in old cars grew I learned to leave the paint work to the professionals, however, I also learned that so called experts can be very light on their knowledge of proper metal prep.
During the time I spent in body repair, the only option for a body filler was 60/40 lead, Bondo and all of it's cousins were still over ten, fifteen years in the future. To use lead as a body filler the metal had to be clean and "tinned". Tinning the metal required muratic acid and heat, once the tinning process was completed, the lead filler could be applied with heat, smoothed with a wood paddle, dipped in bee's wax.
Muratic acid is very caustic, therefore it has to be removed from the exposed body metal and a metal prep applied prior to applying a paint primer.
I have used rust converter/transformers made by several company's for over thirty years on body metal and mechanical parts prior to painting them, or having them painted.
I first learned about the phosphoric acid based "rust transformers" about thirty years ago. I have a nephew that sold chemicals to refiner's, and other commercial paint users. His product was made in Canada, it was absolutely amazing. I used it for years, it made the old "Navel- Gel" look like junk..
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Old 07-29-2017, 12:54 PM   #15
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Default Re: Mouse piss rust

Hey Bill,
Good info, thanks.
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Old 07-30-2017, 09:12 AM   #16
rotorwrench
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Default Re: Mouse piss rust

The tin/lead filling process was always a pita situation. Back in the day, a person could still get mercury based products to tin with. Although mercury was the best, it was a well known poison plus it wasn't any easier to use so folks went to the zinc chloride type tinning material more out of choice for better health than anything. The whole butter idea was so the crap will stick to a vertical surface but it's still a such messy & nasty process if you choose to use it. Being a body man was never a real healthful way to make a living but I've know more than a few that lived into the late 80s or 90s.

One of my mentors preferred to use a build up of the old red oxide lacquer primer rather than tin/lead partly due to material shortages at the beginning of WWII and also during the Korean war even though it didn't have any production time reduction benefits. This sort of forced him to learn to work the metal more plus he became a master of the oxy/acetylene torch. I'm sure glad I had someone like that to learn things from.
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Old 07-30-2017, 12:43 PM   #17
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Default Re: Mouse piss rust

What would mouse piss have the most (damage) impact on, sheet metal or aluminum ?
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Old 07-30-2017, 05:30 PM   #18
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Default Re: Mouse piss rust

Pure 1100 aluminum would fair better than any of the other alloys but all of them are susceptible to corrosion too plus the 1100 isn't really all that good for structures. Structures in airline lavatories get corroded pretty badly over time and have to be rebuilt or replaced. It affects both the aluminum and steel badly. Even corrosion resistant steel will corrode in that kind of an environment.
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Old 07-30-2017, 06:56 PM   #19
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Default Re: Mouse piss rust

Picked up a gallon of phosphoric acid at hardware and it seems to be working great. Will update when i learn and do more. I am tired of learning.

Tim
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Old 07-31-2017, 11:41 AM   #20
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Default Re: Mouse piss rust

I would not suggest the use of "phosphoric acid" as a metal prep, rust transformer. The products that are made for this purpose, JASCO, OSPHO, etc., have other chemicals added to the acid to make it work..
The commercially made rust transformers, metal prep, don't have to be washed,sanded off prior to the application of paint
Hmmmm? "I am tired of learning" I think that when a person gets to that stage in life, it time to lay down and die.
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