Ospho VS. Evaporust

[CJ5Dave]

I saw a product available locally called Ospho. Supposed to prevent rust and prepare for painting. I have been using Evaporust from Harbor Freight and the same product with a different brand name from Auto zone to remove rust. Does Ospho do the same thing as Evaporust, ?

 

[Aukai]

If I'm not mistaken Ospho converts rust to an oxide, the others dissolve rust.

 

[Jim F]

I saw a product available locally called Ospho. Supposed to prevent rust and prepare for painting. I have been using Evaporust from Harbor Freight and the same product with a different brand name from Auto zone to remove rust. Does Ospho do the same thing as Evaporust, ?

No, they are different things.

 

[RJSakowski]

Years ago there was a

If I'm not mistaken Ospho converts rust to an oxide, the others dissolve rust.

That was my impression as well but reading their literature, it contains phosphoric acid and dichromate (think hexavalent chromium for those concerned). They claim it doesn't attack the base metal but elsewhere state it can be used to etch metals.

I have used a product in the past that when brushed on a rusted surface, would convert red rust to black rust, essentially mill scale. It contained a latex polymer which combined with the black oxide, would make a stable coating which could be painted.

 

[Ulma Doctor]

Both Ospho and Evaporust are used for rust abatement, but they accomplish it differently.

I use phosphoric acid almost exclusively now.
Evaporust is fine, it just works slower

 

[pontiac428]

If you want something easy to use that you don't have to watch very closely, use Evaporust. I prefer the passivating/conversion coating from Ospho for most of my personal use, but there is a learning curve to it. Ospho is also a good post-rinse to stop/fix the Parkerizing process.

 

[mmcmdl]

https://www.amazon.com/Loctite-234981-Extend-Treatment-Bottle/dp/B00B73YUKK/ref=asc_df_B00B73YUKK/?tag=hyprod-20&linkCode=df0&hvadid=532916287331&hvpos=&hvnetw=g&hvrand=1303599299131124453&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9007839&hvtargid=pla-1475230474797&psc=1&mcid=0b88d54b50dd3d16b65dcc70fa64f2c3&gclid=EAIaIQobChMI2uSd6LmAhAMVPA2tBh1OegFYEAQYAyABEgKtH_D_BwE

Ive used this in the past and it worked great . Unfortunately all my bottles froze out in the garage and have been scrapped . This turned heavy rust into a black hard surface .

 

[Nesse1]

Ospho lists the active ingredient as Orthophosphoric Acid, which google suggests is just plain old phosphoric acid. I use Kleenstrip Etch and Prep, which is basically the same. Less than $20/gallon from Home Depot, the last time I checked. It works great to derust. You can cut it to dilute a fair bit too, if you want more volume. Evaporust is more mild; if you are derusting a painted part, and want to save the paint to the extent possible, I'd use Evaporust. It does get used up with usage. Phosphoric acid seems limitless, to the extent that I've used it anyway. A sludge will develop on the bottom of the tub, but just pour off the good stuff on top and reuse again and again.

 

[woodchucker]

naval jelly is phosphoric acid, and in my opinion, has been slower than evapo rust. And I have watched different tests on youtube which agree. yet you guys say it's faster????? something doesn't jive.

 

[MikeInOr]

naval jelly is phosphoric acid, and in my opinion, has been slower than evapo rust. And I have watched different tests on youtube which agree. yet you guys say it's faster????? something doesn't jive.

I have used Naval Jelly too and I would guess its thick gelatinous nature impedes a constant fresh solution of phosphoric acid from contacting the rust. With straight phosphoric acid a little bit of agitation speeds up the reaction considerably. A little agitation also speeds up Evaporust.