Part 2 of rust removal

[Herb G]

Some replies to my thread on rust removal have sparked another problem. The cast iron table on my scroll saw is hideously stained from having acid drain cleaner spilled on it.

Is there anything I can do to remove these stains?
I'd like to go back to a nice shiny table if possible.
Thanks for any guidance.

[blackhat]

Sand away the stained metal. It could go pretty deep. Or not. It would be a challenge to keep the table flat if the stains have any depth. A surface grinder could go a couple thousandths at a time and see what you get.

[jbmunro]

I find oxalic acid - Bar Keeper's Friend - useful to remove most stains. Sprinkle it on and use a damp soft scrubby to make a paste and work at it.

[Howard Acheson]

Cast iron is quite porous. It's likely that the material causing the stain has been absorbed into the cast iron and many be impossible to remove.

If you want a "shiny" tabletop, buy a new one.

[Herb G]

I think I'll go with this suggestion.
I need to figure out a way to even it out all over the table though.

[thewizzard]

Herb G said:

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... I need to figure out a way to even it out all over the table though.

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Dump some more drain cleaner on it, spread it around until the entire surface looks uniform, then flush it off. Completely neutralize any acid with a thin paste of baking soda and water. Flush that off, dry it, and sand it.

[Cooler]

thewizzard said:

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[blockquote]Herb G said:

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... I need to figure out a way to even it out all over the table though.

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Dump some more drain cleaner on it, spread it around until the entire surface looks uniform, then flush it off. Completely neutralize any acid with a thin paste of baking soda and water. Flush that off, dry it, and sand it.

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[/blockquote]

If that were an acceptable solution (and I don't think it is) then bead blasting the surface would work better. But the problem with either of these solutions is that it will significantly increase the friction between the surface and the work piece. And I don't think you want that on a saw table.

[Cooler]

We used to "mill" small engine heads by gluing fine sandpaper on a piece of double strength glass and rubbing the cylinder head over the surface. The glass is as nearly flat as anything you can find. Though a 12" square piece of granite tile might do too. But if it does not affect functionality I would just clean it with steel wool and wax it and refer to it as "patina".

[Blacky's Boy]

I've done the same thing only I've used an old cast iron wing from a tablesaw.

[Cooler]

Can you remove the table top? If so you can just bring it to a machine shop and have them grind a couple of thousandths off the top. Or you can get a large piece of double strength glass and stick down some wet/dry sand paper and rub the thing over the glass until it is clean. It should end up flat if you use a large sheet (supported on tabletop) of glass for the surface.