Author Topic: OSPHO metal treatment?  (Read 419 times)

ugly_90

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OSPHO metal treatment?
« on: February 05, 2020, 08:46 PM »
It seems like this stuff has been around since 1947. It's not a paint, an epoxy paint, a grease, oil or wax. Guys have been using this successfully underneath old steel farm tractors and trucks. Procedure is to knock off all rust, coat/spray with OSPHO, it'll deoxodize the metal, turning the rust black, leaving white residue all over which will need cleanup.

Once that's done, the accessible steel shouldn't be corroding for some time. It seems like it might be a viable treatment for assembled lower inside bulkheads, or assembled steel chassis. RRC and Discovery seem to have more rust areas as well to treat.

It's no subsitute for taking something apart and refinishing it, but has anyone been using a product like this before wax or oil spraying under a vehicle? It seems to be aluminum safe.

Red90

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Re: OSPHO metal treatment?
« Reply #1 on: February 06, 2020, 08:32 AM »
Sounds like it is just phosphoric acid.  You can get it much cheaper at a hardware store.  Work it into the rust.  Converts the iron oxide to iron phosphate (the black stuff).  You should then rinse with water to ensure no live acid is left.  Let dry and coat or protect with something.

Be careful on aluminum and zinc (galvanization) as the acid eats their oxides more aggressively.

ugly_90

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Re: OSPHO metal treatment?
« Reply #2 on: February 06, 2020, 10:48 AM »
From what I've read, and I'm sure there's an MSDS out there detailing the contents, it seems OSPHO is mostly phosphoric acid, with some metal salts in there as well, which might be important to its action. It seems like the OSPHO creates a sealed primer surface once cured and dried. The metal salts might be in there to deactivate it?

Off-shelf CLR has plenty of phosphoric acid, is much cheaper, but probably more dangerous to use and dispose. CLR has no deactivation action, you'd have to wash it all off, as you say, and there is no sealant aspect to CLR.

Red90

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Re: OSPHO metal treatment?
« Reply #3 on: February 06, 2020, 01:19 PM »
There is no phosphoric acid in CLR.

The PA is all that matters.  It turns the rust into a phosphate coating.  Ready for painting. Tons of products out there.  All do the same thing.

ugly_90

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Re: OSPHO metal treatment?
« Reply #4 on: February 06, 2020, 02:22 PM »
Yup, no phosphoric acid in CLR anymore, you'll have to look elsewhere. I'll see what I come up with for cleaning up the rear chassis of the 90, a frame-off restoration is not in the cards yet, maybe a three-day rear tub lift and clean.
« Last Edit: February 06, 2020, 03:49 PM by ugly_90 »

ugly_90

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EnviroRust Gel
« Reply #5 on: February 11, 2020, 11:20 AM »
OSPHO and Phosphoric Acid are probably not the way to go for most landrovers, or even steel classic car bodies for that matter.

A product like Evaporust or Lloyd's EnviroRust seems a more reasonable path, with less damage to wiring or alloy, cleanup, disposal and exposure are apparently safer and easier than the phosphoric acid.

Both Evaporust and EnviroRust are available in either liquid or gel. The gelled version may work far better under a vehicle. The EnviroRust is available gelled in a 20L pail, for $200-250 while the Evaporust gel seems like smaller containers. Lloyd's EnviroRust is made in Canada.