Phosphoric acid dip to clean rusty hardware

[RenoHuskerDu]

Started stripping and cleaning this new $700 acquisition today. 1986 250 with a 6.9 and T-19. Found in a farmer's field, 85k miles on her. Rust had frozen the seat tracks but I pulled the seat and freed them up. Broke two seat bolts in the floor so I popped out the little holders that the bolts thread into.

All hardware is soaking overnight in Ospho, a liquid phosphoric acid solution. I find this a miracle for rusty old hardware. After a day, it comes out dark and rust free. The dilute phosphoric acid converts ferrous oxide (Fe2O3) into ferric phosphate (FeP04), which inhibits future rust and is a good primer before painting, or even not painting. We use the heck out of Ospho here on the ranch, for gates, fence posts, bare metal flatbeds, tractor parts. I'll use Ospho on the small rust patches in the floor after pulling the carpet.

But when I use Ospho as a dip to soak rusty bolts, a floating black layer of spooge always forms on the top. I wonder if we have a resident chemist who can explain that occurrence. It looks like oil, in fact it may be residual ATF from the ATF/acetone 50% mix that I use as penetrating oil. But of course AFT is bright red.

[rcarlisle]

Where does one purchase Ospho?   I'm replacing a lot of rusty screws, so if I had a way to refurb screws that aren't terribly damaged, that would be cool to me.  Much better than having to stop and go buy more screws when I figure out what it needs.

[ArdWrknTrk]

Randy, Ospho is a brand name like Aspirin, Kleenex or Bandaid, that has entered the lexicon.

You can find Klean-Strip "Concrete and Metal Prep" at either of the big box stores.

https://www.lowes.com/pd/Klean-Strip-Concrete-and-Metal-Prep-1-GAL/1001456348?cm_mmc=shp-_-c-_-prd-_-pnt-_-google-_-lia-_-133-_-thinnersandsolvents-_-1001456348-_-0&store_code=3248&placeholder=null&ds_rl=1286981&gclid=Cj0KCQjwytOEBhD5ARIsANnRjVih6UAxJ-3nYGrsaGzYVPyMWUkgKUuxgaC1-DojD5V2CXprQ5gGKN8aAh63EALw_wcB&gclsrc=aw.ds

[66gtk]

Eastwood sells Fast Etch.  Same thing, I think.  I use it quite a bit for similar reasons.  

[Machspeed]

Exactly, Jim! Use the Klean-Strip all the time. It cleans and coats.....great thread.

[RenoHuskerDu]

Use caution when using rust removers. Some formulations contain hydrofluoric acid which is extremely dangerous. It can penetrate the skin, destroy bone and cause a heart attack without your knowledge. Be sure to read the label on the product you intend to buy and steer away from products that contain hydrofluoric acid. Ospho label shows none of that.

Here's the MDS

http://www.ospho.com/images/OSPHO%20SDS%20COLOR%202019.pdf

[ArdWrknTrk]

I haven't seen hydrofluoric acid in consumer products except ones meant to etch glass.
We get tankers of it at the water treatment plant because they can counter the base of hypochlorite and add fluoride at the same time.



http://www.kleanstrip.com/product/concrete-and-metal-prep
Nope,  nothing but 38-44% phosphoric acid, water and color.

[RenoHuskerDu]

Seems about the same as Ospho in percentage by weight.

So does anybody know about the layer of black that forms on top?

[ArdWrknTrk]

I always just assumed it was iron and contaminants that the acid got under and lifted off while the parts were pickling.
Even if it was ATF I'd expect any kind of oil to be completely 'burnt' from the acid.

What always amazes me is the amount of sludge and foam I get from electrolysis.
I know it only started out with washing soda but I highly expect the cell is creating more than just hydrogen.
I need to test the PH next time I get a chance to do that.

[FuzzFace2]

ArdWrknTrk wrote

What always amazes me is the amount of sludge and foam I get from electrolysis.
I know it only started out with washing soda but I highly expect the cell is creating more than just hydrogen.
I need to test the PH next time I get a chance to do that.

When I did electrolysis I did it big, made a pool 6'x6'x3' deep to do the hood & fenders of my Javelin.

For nuts & bolts I soaked them in something like "rust be gone" I got through 1 of the parts stores.

I did use the acid on the frame and the body on the heavy pitted rust with a spray bottle before painting frame and doing body work.
Dave ----

[ArdWrknTrk]

I usually use a joint compound pail but I have a bright blue kiddie pool that I did a speedway motorcycle  frame in.

Anyway.... The phosphoric acid is always effective at reducing iron oxides and leaving some protection.
After rinsing and drying, light oil is good unless you are going to paint right away.

[RenoHuskerDu]

Here are pics of what I'm getting in the little dip bottle after cleaning about 15 bolts.  I'm suspecting that the white precipitate that forms on metal sheeting after brushing on Ospho is the same material that is turning the green Ospho into a milky green slurry.  I suspect that this Ospho has done its life purpose, and needs to be renewed, as it were.



Here are the results, seat mounting hardware from the F250 in my first post.
After drying, they will retain the dark gray appearance, and resist rust well.

[ArdWrknTrk]

Wow.  It looks like you're soaking them in ranch dressing or spinach dip!  🤣

I get the white crust on items if I don't properly rinse them, but I've never seen the dilute acid emulsify like that.

[RenoHuskerDu]

I'll get you some nice chips, then call the paramedics

It all started off nice clear green, a few weeks ago....

[FuzzFace2]

Little bigger that the kiddie pool

Fender & bumper brackets

I did 2 other fenders and 2 hoods in the pool.
Dave ----

[ArdWrknTrk]

I think I saw those pictures over on FTE.

Just stay away from chlorine and sulfur salts as electrolytes, for obvious reasons.

[RenoHuskerDu]

Wow Fuzzface, my wife would kill me.  Hats off to you. All my old bumpers in the bumper graveyard yearn for similar treatment.

It looks like you're in a suburban setting too.  I'm VFD, we would get called out for this kind of setup if a Karen spots it in city limits. Keep it discrete.

[ArdWrknTrk]

What could someone possibly say about it?

[RenoHuskerDu]

The petty issues reported in today's EMS and Fire calls would shock you.  Many counties are encrypting so it's harder to hear traffic. Ours go out only thru data to our phones. So nobody can hear some lady complaining that she has anxiety so she needs an ambulance. Or the neighbor has a funny smell.

[ArdWrknTrk]

I honestly don't want to be a part of this experiment any more.