Mill scale removal

A dip in phosphoric acid should provide the surface you desire. If you can't buy phosphoric acid, buy some Naval jelly and use that. It's buffered phosphoric. I suggest you leave the phosphoric on it long enough for it to change the surface of the clean metal, don't just whisk it through. I've refinished a few steel doors that way, and the surface left is somewhat darkened and does not rust, not even when permitted to sit unprotected for a few days. Didn't try it with water being left on the surface, but I did rinse with fresh water and wipe dry. Not a trace of rust, unlike anything that is cleaned with HCL (muriatic acid). There's some kind of conversion that takes place with the iron (steel) that I am unable to describe, considering I'm not a chemist. The surface is slightly darkened, a sure sign you've created some kind of skin that is far less reactive to oxygen.

Good luck

Harold

That would surely be a thin strike coating of iron phosphate .. - GWE

That's sort of what I figured, too. While it may not be exactly the same thing, I can't help but think it's on the order of Parkerizing. Not pretty, necessarily, but rust resistant, which is the objective.

Harold

Harold I will give that a try. Thanks for the info and I hope you can get Meyers the glass man to see the error of his ways.

Steve Peterson Kettle River Ironworks

You're most welcome, Steve.

Went to your web site and enjoyed looking at the cool items offered.

Myers. I'd love to succeed, but when a person uses his considerable success to mask his wrong doings, it's damned hard to get anyone to take a serious look at what has happened. We're not giving up, though.

Those that are hard working and honest dealers should be offended the most by actions such as his. What he's done is no different from people that pass bad checks, which then make anyone that uses checks suspect. Through his criminal actions he makes all people that sell on eBay suspect. That's not fair to those that have high principles and treat the customer with respect and fairness. I'd hope that the honest people would more or less band together and try to clean up the crooks, but it appears that not everyone is sympathetic of those that get cheated. In some small way, they seem to condone the actions of those that victimize honest people. Hard to understand, at least for us.

Good luck with the metal finishing, Steve. We'd all like to hear if it works for you. Please let us hear from you again.

Harold

I have been toying around with this stuff called Oxisolv that is sold by Eastwood to do something roughly identical to what you're trying to do. It seems to work pretty well so far... one of these days I'm going to subject it to a salt spray and see how well it survives to really test it out. It's this oily liquid that smells as though it has a healthy dose of phosphoric acid in it, but in addition to eating off the rust it also leaves a thin layer of zinc over the surface of the metal. In my tests so far I've found that the layer isn't thick enough to cause any problems with welding, but it does look like it prevents rusting for a while. It also seems to eat the dirt and crud off, though it is a little bit of a pain to clean the Oxisolv off once you're done with it. Eastwood suggests cleaning it up with their "PRE" paint prep product, and that does seem to do the trick without too much elbow grease.

I've been using it to clean up slight amounts of rust on some cold rolled sheet prior to welding. I have found that it also eats off the heat rainbows caused by grinding and welding, which is a nice plus. I've started steel brushing my MIG welds and then spraying them down with the Oxisolv, which seems to clean them up quite nicely and keeps the rust off until I can primer and paint the things. It doesn't seem particularly effective against mill scale, but with a suitable application it does eat the rust away.

Oxalic acid is available in granular form labeled "wood bleach" check the label to be sure its Oxalic, Phosphoric Acid is available at Home Depot as Concrete etch its in the pain department. Alan Black

I use a product called "Ospho." It is a mix of phosphoric acid and metal salts of some kind. I've also used Jasco "Metal Prep" and prefer it to Oshpho, but I cannot get it around here. The two products are basically the same. You should be able to get one or the other at any full-service paint store.

I've had very disappointing results using straight phosphoric acid. To illustrate: I went to a lot of trouble to abrasive blast a set of steel wheels for an antique engine. I had one extra, so I just painted it with phosphoric acid and let it sit.

Big mistake! It rusted with a vengeance!

On the other hand, I have hundreds of items awaiting painting that I've treated with either Ospho or Metal Prep. Some of them have been sitting here for five years and not a one has shown a bit of rust.

I've got to temper remarks by saying we live in a very dry climate. I have no idea how long it would take for an Ospho-treated part to rust in high humidity.

Regarding removing your mill scale, I hear that a vinegar/salt solution works very well. It isn't nearly as nasty as hydrochloric acid. I use HCl, too, for some jobs, but it is darned hard on the lungs.

Regards,

Orrin

That's an interesting observation, Orrin. I think it's Ace hardware that sells the Ospho primer. They say to paint over rust just like you would with any kind of primer, and then top coat with paint. I did that to our

1,100 gallon heating oil tank and now I have an 1,100 gallon rusted tank. In some weird way, it is worse than nothing, yet when I used concentrated phosphoric acid (I bought a 5 pint bottle to clean our ice machine) when I was painting the shop doors it does a great job. The conversion film it leaves on the surface isn't much, more a discoloration than anything, with somewhat rainbow colors when light hits it. Could be the key to success is getting ALL of it off before moving to a second process. Dunno. I think that overall, phosphoric is the best choice, but I'm thinking there's more to it than just the phosphoric. If one could learn the Parkerizing process, I think this would all make sense. It's been good enough for the military for a long time.

I sure agree with HCL and lungs. I used to use it by the drum when I refined precious metals. I learned to pour it only with the fume hood running. Nasty stuff!

Harold

You might also try phosphoric acid that has Zinc disolved in it. It should remove the rust and replace it with zinc phosphate. Excellent surface for painting. That tip is from a book on surface preparation.

Dan

Harold,

Parkerizing is relatively easy, provided you've got a tank large enough for the item, as it must be submerged. Check out this link for info:

I've tried it on small parts and it works like a champ.

Bob

Any tips on using this stuff? How do you apply it?

I brushed it on some parts that were later primed and painted, and I was a tad disappointed in the paint's adhesion. The Metal Prep foamed a bit, and the bubbles dried and left some texture there. I rubbed off the build-up with a hand pad, but probably missed some spots. Thought maybe that was the cause of some paint flaking that occurred. The metal under the flakes was clean, though; not rusted.

Jim

On Wed, 12 May 2004 12:58:12 -0500, "Steve Peterson" vaguely proposed a theory ......and in reply I say!: uncap my header address to reply via email

Sorry? I do have a vested interest in defeating a set entity.

Seriously.

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Sometimes in a workplace you find snot on the wall of the toilet cubicles. You feel "What sort of twisted child would do this?"....the internet seems full of them. It's very sad

I follow the directions of whatever the product. It runs in my mind that the instructions for Metal Prep said to flush off the excess and dry before painting. The Ospho directions say to leave it on and use it as a primer. I've never been entirely confident of the results if I do it this way. If it's a steel part, I'll brush it on and let the stuff react with the base metal, but before it dries I either wipe off the excess with a lint-free rag or paper shop towel; or, blow it off with compressed air.

In my experience, Ospho works differently on cast-iron as opposed to steel. It reacts vigorously with cast-iron and quickly becomes "used up." I generally like to blot off the excess almost the instant I apply it.

Back in about 1980 I had to replace the hood on my pickup. I used a metal prep type of product that was to be brushed on and wiped off. I wondered how the paint would perform. But, I saw the truck about ten years after I traded it off and it looked just fine: no chips or peels, anywhere.

I'm still not sure about paint adhesion with Ospho underneath; but, in our dry climate it has never let me down. Some day I hope to run some test coupons just to satisfy my curiousity.

You pretty much addressed it the way I was thinking, Orrin. Anywhere I left the Ospho as primer, it has bubbled and rusted something fierce. How I wish I'd have used it more as a prep, wiped, or otherwise removed it, then painted.

My advice? Don't try it, not unless you do it on cast iron as you suggested. I'm thinking I'd have had good results that way. Sure didn't work well on steel.

Harold