• Hello there guest and Welcome to The #1 Classic Mustang forum!
    To gain full access you must Register. Registration is free and it takes only a few moments to complete.
    Already a member? Login here then!

Ummm...WTF?

A

AtlantaSteve

Active Member
OK so I had a little surface rust on some of my floorpans. I have patched the parts that were rusted through or too thin to keep, but some of it is just surface rust.

So I have some 1:1 Phosphoric Acid:Water mix, and I sprayed it on the pans and walked away...I came back 10 minutes later expecting to see some converted rust that turned black.

It had instead turned white! It looked like it had a dry, chalky coat over anywhere that had rust where I sprayed. Sort of like a rapid oxidation.

So two questions:
1)What is this? This is my first experience with phosphoric acid, but I sure didn't get the results I'd expected
2)What should I do about it? Is it alright? Or should I sand or wire wheel it back off?

Thanks

Steve
 
I've never used phosphoric acid that I'm aware of. I have used POR-15 Metal Ready, though, and it turns white as it etches the rusted areas. Based on that, I'd guess that you're fine. Wash it off and treat it with a rust encapsulator.
 
I use phosphoric acid. It should be mixed 3:1 water to acid to get the proper effect. What you are seeing is simply the result of acid drying.

You have to have all the crunchies knocked off for it to do the turn black thing.
 
3:1? grr. Well I KNOW I've seen people who used 1:1 mixtures...is that for something different? (like maybe cleaning up old bolts?)

OK so I can't seem to wash the powder off. I scrubbed it good, wiped it up, and as soon as it dried, it dried back to the chalky consistency...I assume I need to get this junk up before I hit it with any rust encapsulator, right? I hit a small part of it with the wire-wheel and that seemed to get it up..guess that's my only option?

Thanks for the info John and Sluggo

Steve
 
"AtlantaSteve" said:
3:1? grr. Well I KNOW I've seen people who used 1:1 mixtures...is that for something different? (like maybe cleaning up old bolts?)

OK so I can't seem to wash the powder off. I scrubbed it good, wiped it up, and as soon as it dried, it dried back to the chalky consistency...I assume I need to get this junk up before I hit it with any rust encapsulator, right? I hit a small part of it with the wire-wheel and that seemed to get it up..guess that's my only option?

Thanks for the info John and Sluggo

Steve
Click to expand...

No, you have other options. 80 grit, 180 grit, 220 grit, etc. Depends on how hard you want to work :dumas

I use it full strength for ugly sh!t but you have to rinse it with water before it dries. You should rinse it regardless.
 
I've scuffed the white residue and shot DPxxLF primer over the top of it just fine.
 
You must log in or register to reply here.
Back
Top