Rust Convertors

[gumboil]

Anyone know whats in these so-called rust convertor/primer liquids sold in shops like Halfords?
I took off the rust on a garden trowel earlier this week with wire wool and worked the stuff well into the surface. gave it 2 coats.
The trowel looked like part of it had not been treated after using it just once for light work (patches of the stuff missing). Today I've been able to peel off the stuff just like paint on a badly prapared surface.
I know I took off all the rust and the trowel was dry and had no grease or oil on it.
Anyone got any idea what went wrong? What does this stuff contain? How are they supposed to turn rust to metal? Why does the stuff turn my fingers black?

[Catso]

I don't think they'll do what you think they will!

They're intended to be surface preparation, prior to painting. As you're applying them to metal, which isn't porous, they can only work on the surface. When you used the trowel again, you removed the surface, and it started going rusty again.

They contain some sort of phosphoric acid (or something like that) I think. It reacts with the iron oxide (rust) and turns it into some other iron compound. It doesn't turn the rust back into pure iron. It also reacts with your skin, turning it black. It doesn't wash off.

[gumboil]

The Turtle Wax one I used did say that it "converted " rust to metal, but it didn't say what sort of metal or that it was only on the surface. I think this is a bit naughty of the manufacturers as it can't be much use on a tool etc that's going to be used. Perhaps its only for show.

It has to be working only on the surface as you've said Catso.
Two of my fingers are still stained black with the stuff and you're right -it dosn't wash off.

Thanks

[gumboil]

Thanks EDDIE51.

This could be where I went wrong! I think I'll do as you suggest and take it back to bare metal and then paint it, probably with a couple of coats of Hammerite.

Thanks again.

[Toureman]

You have spent a lot of money on rust converters and paint why don't you spend less and buy a stainless steel trowel?

[gumboil]

Picked up the rust converter free at work and I had the Hammerite knocking about in the shed Toureman. Can't get much cheaper than that.

It's a family heirloom and I'm too sentimental to get get rid of it. It's been in the family for years.

My father changed the handle a few years back and I recently changed the blade!

[Gef]

To turn rust (iron(III) oxide) back into iron you need a blast furnace (or equivalent). Any household product which claims to do this is a fake.

[Zevon]

Not necessary a blast furnace, it could easily be done with aluminium powder, or a more reactive metal, heated with a bunsen or blowlamp, the problems are:-

Buying the chemicals needed.

Anything above aluminium is a bit too reactive to be used safely

Even with aluminium the iron would melt and any wood or plastic would char, melt oir catch fire.

Still you'd be back to pure iron.

[Gef]

Zevon, I did say a Blast furnace or equivalent. The reaction you describe is called the Thermite reaction and it is used, in situ, to weld railway lines together.

[Zevon]

But doesn't require a huge blast furnace, super heated pure oxygen, limestone or taps to remove slag. it could happen in your back garden with your trowel, blast furnaces need to be much hotter as they use cheaper carbon instead of aluminium, aslo the carbon forms impurities thart need to be removed. HEnce the complexity of the blast furnace.