Removing Dark Patina from Cast Iron?

tobnpr · Oct 13, 2017

For no real reason, decided to try to make my backplate, dog plate and dogs a little prettier :nutter:

Degreaser doesn't do it (Purple Power), is there a way to remove it? Considered spinning the plates on the lathe and carefully using Scotch Brite; perhaps bead blasting (for the dogs)?

gzig5 · Oct 13, 2017

If you take a fresh cut across the surfaces you'll expose fresh material that will be shinier. Depending on the quality of the CI it may end up a bit "hairy" too. I just did this on a face plate and it ended up shiny and hairy, but flat enough for my purposes. Wax may help prolong the look. Bead/sand blasting will turn it dull gray in my experience. In the end it isn't worth the effort. If you want it shiny and silver for a long time buy a new plate to look at or paint it.

Conrad Hoffman · Oct 13, 2017

I think of them more like a cast iron fry pan. They get "seasoned" over the years and I just tune them up with a bit of oiled Scotchbrite every few years.

DMF_TomB · Oct 13, 2017

tobnpr said:
For no real reason, decided to try to make my backplate, dog plate and dogs a little prettier

Degreaser doesn't do it (Purple Power), is there a way to remove it? Considered spinning the plates on the lathe and carefully using Scotch Brite; perhaps bead blasting (for the dogs)?

.
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i work with fixtures and parts weighing tons. nylon abrasive and a coarse bench stone removes rust after you wiped any oil or grease off. then i wipe with alcohol rag and stone with a fine stone. rust and oil coolant the stone will not go over smooth. you will feel something is there. keep working at cleaning, stoning and eventually it stones smoothly
.
nylon abrasive pad in a 2 or 3" right angle air grinder speeds things up on really rusty stuff.

sfriedberg · Oct 13, 2017

ScotchBrite or other non-woven abrasive pads. Generally four choices for how aggressive you want the grit to be. Rub with oil, makes a big difference.

CWC(4) · Oct 14, 2017

You might try Evapo-Rust or similar product. There are a few products out there including one made by WD-40. These work pretty well with rust or like kind discoloration and are pretty much non-toxic watery solutions that you just soak your parts in for a few hours or overnight and parts come out looking pretty clean.
CWC(4)

Rex TX · Oct 29, 2017

+1 on Evaporust. It is very good at removing things other solvents won't touch, like hardened coolant, while not harming paint. One other thing I use a lot is automotive wheel cleaner. Get the type that says " All wheels" or safe for painted wheels. If that won't get it off then Evaporust will

texasgeartrain · Oct 30, 2017

I use wd40 and a fine grit sandpaper or emory cloth, like 320 to 600 grit. Spay down the work and sandpaper, it won't leave scratches this way. Just wipe it off with a rag when done. Comes up nice imo.

jwearing · Oct 30, 2017

Am I the only one that likes the patina?

It seems like bright, fresh iron rusts more easily.

Also I think darkened iron looks better, like the machine is a workhorse with some experience.

Blazemaster · Oct 30, 2017

Sometimes I use solvent and very fine steel wool, seems to brighten it up a little

Dobermann · Oct 30, 2017

I've read this thread from day to day, wondering...why? Why go to all that trouble when the "patina" or modest oxidation will just come back? It'll be a never-ending occupation unless you clear-coat the pieces after polishing them up.

Vladymere gr · Oct 31, 2017

Doberman,

I think people do this because "bright metal and new paint improve function, performance and accuracy" on old iron.

Vlad

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Removing Dark Patina from Cast Iron?

tobnpr

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sfriedberg

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jwearing

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