BUICK 1964 Skylark Coupe Project

[ck80]

Okay, now you have me interested. Can the oxalic acid be applied using a compressor and a cheap gun? What about the Phosphoric? If not by air, what about using one of those 2 gal pump bottles like what get used to apply liquid weed killer or fertilizer?

As for the body wax, 3M makes a version of that which comes with a extension kit of various lengths of tube that fit to the bomb and can get into tight or deep places.




Nick

The oxalic acid is the main active ingredient in products that try to eat the rust away to leave a relatively clean finish. Its used for everything from dissolving mineral or rust stains in industrial cleaners to lightening wood to rust dissolving netal prep products. It can be washed off after and is environmentally neutral once dilluted. You'd usually use a brush designed to resist the acid, or a pump sprayer, usually plastic. You can buy it in a powdered form and dilute it with water to desired strength.

The phosphoric acid is the main active ingredient in most all products that claim to 'convert rust' and it works by having the iron oxide (rust) react on the molecular level with the phosphorus in the acid to create an iron phosphorus layer, which is the 'black' color left behind. Downside to the phosphoric is it an only react to whatever level it penetrates to. Deeper rust may not get "treated/converted" and thus the rust returns after, which is why people will complain 'that naval jelly fix didn't hold up...' it's also used in all sorts of things, and, you can cheaply buy gallons of it in a food-grade 85% concentration. It's also present in things like coca-cola.

If you read into any of those products, ospho. Evaporust etc you're going to find one, and sometimes both, of those acids present as they're the active catalysts. Difference is, the 'rust converter/rust eater' products can be $130 for a diluted version of what you can buy the concentrate of the acid itself for like $20.

If the loose rust is knocked down with a flap wheel or wire cup, then the oxalic sprayed maybe even a couple coats then cleaned with water, then attempt to 'convert' whatever is left behind, then you just some paint followed by the wax to inhibit moisture, odds are you don't see much of anything return.

It's what I did to some of those early 80s paint/primer defect vehicles in my new england years to stop the rust that formed in the exposed primer, painted it, and nothing came back with over a decade of winter driving.

 

[joesregalproject]

That inner-roof flash rust is probably the rule rather than the exception on old GM stuff.

My brother used Ospho in hard to reach spots on a couple past projects. He painted it on with an acid brush. I don't think it was necessarily a product that he searched out, just found an open bottle at work and swiped it. Honestly, I can't say how permanent the solution was because both cars were sold shortly after they were finished.

I wouldn't doubt the surface rust on the inner roof is common. Minimal paint plus condensation plus a headliner to hold the moisture in; it's a recipe for rust.

Rust Mort is phosphoric acid based, I don't know how similar it is to Ospho. I know it is a lot more expensive. I've used it for pits that were too deep to grind out with a carbide burr or a die grinder and it does work well. I've just never used it on big areas of surface rust. But the pics of that car on Jalopy Journal look promising.

I've really never worked on rust quite like this. Usually I'm dealing with small, concentrated areas of rot, not big areas of light surface rust.

 

[DRIVEN]

To be fair, that's more of a high desert sunburn than rust.

 

[ck80]

To be fair, that's more of a high desert sunburn than rust.

That's probably California rust, which is similar to the high desert stuff, and, what we get here in Georgia on the top sunbaked surfaces. The nice thing is it doesn't pit the metal usually.

 

[DRIVEN]

Considering that Skylark is almost 60 years old, it looks pretty good.

 

[ck80]

Considering that Skylark is almost 60 years old, it looks pretty good.

Better than most 60 year old women look.., that's for sure. Better put a ring on that one Joe

 

[CopperNick]

Since I have to dig back into the box outer fenders on the S-10, AGAIN, now thinking that the Ospho Rust Mort combination might be an answer. How inert are they post application to being exposed to MIG wire?

Also, any suggestions on sourcing the Oxalic Acid in powder form? Body Shop Supply? Hardware Store? Industrial Supply? ??????





Nick

 

[ck80]

Since I have to dig back into the box outer fenders on the S-10, AGAIN, now thinking that the Ospho Rust Mort combination might be an answer. How inert are they post application to being exposed to MIG wire?

Also, any suggestions on sourcing the Oxalic Acid in powder form? Body Shop Supply? Hardware Store? Industrial Supply? ??????





Nick

I know down in the states the powdered oxalic is as easy as an amazon or Walmart.com outside-vendor order, but, it's a ups-ground delivery as hazardous material. It also gets used as a final polish material for marble slab so some industrial supply places would carry it, key thing being keeping it DRY. My guesses would either be industrial supply, or, chemical supply since it's a little above your hardware Store do-it-your-selfer level of so many idiots out there who would breathe in the powder mixing it or leave it on a damp floor making too many issues of liability.

For rough equivalency purposes, it's about 10,000x stronger than say white vinegar as an acid, which means you want to dilute it down with a good amount of water when done. So, to make up numbers, say you wanted a 10% solution in two gallons of liquid, by the time you cut that with 500 gallons of hose water, you're probably looking at having roughly 502 gallons of white vinegar to dump out. That's a setup where you take a 5 ft wide $10 season end closeout round hard plastic kiddie pool at Walmart, spray the part down while it's standing in the pool, and rinse using a non-pressurized (no nozzle) garden hose till the pool is full worth of water. At that point it'd be like having a pool worth of white vinegar strength acid. I wouldn't pour it on your lawn, but, on the driveway that you then rinse down with the hose? Relatively harmless. Point being, there shouldn't be any oxalic left behind on your treated surface after it's thoroughly rinsed/flushed away. The heavier the rust the longer you want it to stay in contact with the rust. I used it over afore mentioned kiddie pool on high (90%+humidity day) in shade where I'd spray it down with the bottle every so often to keep it from drying but let excess drip off on things too big to submerge into a pail of it.

As far as the phosphoric, basically you're self etching the steel surface. What you lose in that process is if any over the counter product adds any metal salts designed to be deposited on the submerged metal beyond the chemical conversion side of things as straight acid without extra metallic salts. I'm not sure how all various mig fluxes would react as I'm no welding expert, but, I remember basics for steel which warned surface welds on high phosphorus steel would be brittle and crack prone. If it were me making a guess I'd do a quick grind on the surface right at the weld location to strip the coatings off when I wanted to do it, spray a weld through primer over, weld, and paint as opposed to welding through a iron phosphate coating, even one from an over the counter product, just to keep the product from getting into the welds and having whatever weakness that could add??? Again, that's an issue with any product using that phosphoric acid in it.

 

[joesregalproject]

I removed the windshield today. It was attached better than the rear window but not by much. Someone resealed it at some point with some nasty butyl or similar adhesive. The glass is delaminating so I probably won't reuse it. The window frame is in excellent shape.

Since I have this Rust Mort sitting here, I decided to create a couple test areas. Some areas I just brushed it on, others I scrubbed. You can pretty clearly see where I scrubbed the Rust Mort on the package tray on the passenger side as well as on the roof. I'll let it sit there overnight and see how it looks tomorrow.

 

[CopperNick]

If there isn't a layer of paint or primer acting as a barrier, the test section should turn black. I did the upper duct panel on the Monte's rad scoop and found that, if I used a fine grit flap wheel or a fine wire wheel on the metal to strip off the overburden, that the remaining embedded rust responded quite well to an application of the Rust Mort. I went heavy, meaning that I slathered the stuff on to make the surfaces completely wet. Did one side, let dry, and went for the other. I have even applied Rust Mort, let it dry, and then sanded it down and re-applied it in cases where the surface seems to "bubble" or craze. The deeper you can get it to penetrate the pores of the metal, the higher the kill rate on the rust will be.

Thanks for the detailed answer on the Ospho and the mix/ratio example by way of amplification. What I would be looking at is about one tablespoon of the dry Oxalic Powder to around Five gallons of water and use a plastic garden pump bottle to apply it. Did have a chat with the owner at my Neighourhood Auto Supply Shop and he noted that almost as soon as the stuff is applied and bare metal starts to appear, it needed to be neutralized with water, dried thoroughly, and hit with a primer/rust sealer.

As matters stand i do happen to have a childd's "never been used" wading pool on hand as one project for last summer was to have been a rust removal exercise using industrial/feed-grade molasses. It didn't happen but I still do have the stuff in a 5 gallon pail with a nice tight lid on it out in the shop.



Nick