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  1. #1
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    Default Cleaning rust off a cast iron machine table

    Hi all,

    I am refurbishing a vertical bandsaw. The cast iron table is in good condition but orange with rust. What is the best way to get it near new condition again but without removing too much material?

    I thought gentle abrasion with scotchbrite pads vs phosphoric acid but will the phosphoric acid etch into the surface and do some damage?

    Ignore the parts in the pic, it's just to show the table.

    TIA!

    20190808_214806.jpg

  2. #2
    Join Date
    Aug 2011
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    The best thing I have found which removes all rust but very little (if any) metal is soaking the parts in a solution of 1 part molasses and 9 parts water.

    Only down side is you need to soak it for about 2 weeks. However when you remove the part and wash it clean it's as clean as you will ever get. You need to remove any grease or oil first otherwise it won't work.

    You can buy 5kg tubs of molasses at stock feed places for about $10. The solution can be used many times over.

    I had a large part I wanted to clean (jointer planer table) so I made a box out of bricks in the backyard and lined it with a tarp. Pre-mixed the molasses in a bucket before pouring into the tarp and topping up with water.

    Cheers.

    Simon

    Sent from my SM-G970F using Tapatalk
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  3. #3
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    Default

    I'd be tempted to put an orbital sander on there. With gentle pressure and moving it uniformly across the table, I doubt that any variation in the finished surface would be noticeable. Plan B would be some Evaporust on paper towels.

    Michael

  4. #4
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    My personal preference is a steel scouring ball (the ones you scrub pots with, NOT steel wool) because it leaves a nice patina behind which a) I like the look of and b) seems to resist re-rusting better than if you take it back to bright metal.

    I think I've heard that citric acid solution works quite well, but it needs a while to soak which might not be practical if you have to try to find a container large enough for the table to fit in.

  5. #5
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    Apr 2018
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    Default

    Thanks everyone for the quick replies.

    Quote Originally Posted by simonl View Post
    The best thing I have found which removes all rust but very little (if any) metal is soaking the parts in a solution of 1 part molasses and 9 parts water.

    Only down side is you need to soak it for about 2 weeks. However when you remove the part and wash it clean it's as clean as you will ever get. You need to remove any grease or oil first otherwise it won't work.

    You can buy 5kg tubs of molasses at stock feed places for about $10. The solution can be used many times over.

    I had a large part I wanted to clean (jointer planer table) so I made a box out of bricks in the backyard and lined it with a tarp. Pre-mixed the molasses in a bucket before pouring into the tarp and topping up with water.

    Cheers.

    Simon

    Sent from my SM-G970F using Tapatalk
    Simon... I've never tried molasses but have used electrolysis for rust removal. The catch is this is a big bandsaw (90cm throat) and I was hoping to leave the main table in place and work around it, however I'm probably just being lazy.

    Quote Originally Posted by Michael G View Post
    I'd be tempted to put an orbital sander on there. With gentle pressure and moving it uniformly across the table, I doubt that any variation in the finished surface would be noticeable. Plan B would be some Evaporust on paper towels.

    Michael
    Michael... The orbital sander makes me nervous but I might be over protective.... It might actually help make it flatter after years of factory use. The Evaporust looks promising, it is rumoured to be EDTA and hence no acids etc. It's available in a gel form too so won't need the paper towels.

    Quote Originally Posted by elanjacobs View Post
    My personal preference is a steel scouring ball (the ones you scrub pots with, NOT steel wool) because it leaves a nice patina behind which a) I like the look of and b) seems to resist re-rusting better than if you take it back to bright metal.

    I think I've heard that citric acid solution works quite well, but it needs a while to soak which might not be practical if you have to try to find a container large enough for the table to fit in.
    Elan.... Yeah I'm always puzzled why those scouring balls don't seem to scratch pots and pans, good idea.

  6. #6
    BobL is online now Member: Blue and white apron brigade
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    If you want something a lot faster but just as safe as molasses, try citric acid, vinegar or oxalic acid. Oxalic is the industry standard - its fastest at converting the rust and produces the the most rust resistant surface behind. Citric and vinegar are slower but still quite effective. Phosphoric acid (PA) is also quick.

    Any residues left behind by these acids are usually easily rubbed/washed off in these solutions.

    Whatever you use DO NOT use any water to remove the residues or residual acid as this just restarts the rusting.
    Let the excess acid drip off the part, blow dry the parts with a compressor, and then apply some light machine oil or wax.

  7. #7
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    Hi Guys,

    I would second citric acid / Lemon juice ! I've tried it and I'm now a believer.

    I'm sure you have seen my pictures of the number stamps that I found rusting in the local scrap yard and the rusty slitting saw blades that I bought last week. They had 36 hours in pure lemon juice. That stuff is great. here in the UK its 29p for 150 ml bottle from Aldi. I reckon that a paper towel soaked in the stuff would work just fine on your saw table.

    10-07-2019_005.JPG 10-07-2019_006.jpg
    This is the stuff, made in Italy.
    Best Regards:
    Baron J.

  8. #8
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    I'd use a wire cup brush, get one of the less aggressive twist ones and run it against some scrap for a few minutes to flex the wires into shape then have at it on your table. Don't push too hard, go easy on the corners and you'll end up with a nice rust blued finish.
    When your done rub on some linseed oil and it'll be as good as gold.
    Cheers,
    Greg.

  9. #9
    Join Date
    Oct 2015
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    melbourne
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    Quote Originally Posted by simonl View Post

    You can buy 5kg tubs of molasses at stock feed places for about $10. The solution can be used many times over.


    Cheers.

    Simon
    Only if you cover it...
    My bucket of molasses just 'disappeared' when I wasn't watching...

    No leaks, no residue.
    I assume something drank it Cleaning rust off a cast iron machine table

    (and it's best if it is not near a window.. It's odour is "distinctive"...

    Russ

  10. #10
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    May 2011
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    I use Inox and an orbital sander, on a lathe I had stored for a few months under a carport.
    Prevents any further rusting too.
    Kryn
    To grow old is mandatory, growing up is optional.

  11. #11
    Join Date
    Apr 2018
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    Lismore Northern NSW
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    Thanks everyone!

    It seems there is more than one way to skin a cat (as long as it is a rusty cat). So we have:

    Mechanical abrasion
    sander
    scouring ball
    wire brush

    Reducing agent
    molasses
    electrolysis

    Chelation
    Evapo-rust

    Acid attack on rust
    citric
    acetic
    oxalic
    phosphoric

    I would prefer to not remove the table and I might try the Evapo-rust on kitchen paper and see how it performs.

    Thanks again!

    Steve

  12. #12
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    Dec 2013
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    Quote Originally Posted by Michael G View Post
    I'd be tempted to put an orbital sander on there. With gentle pressure and moving it uniformly across the table, I doubt that any variation in the finished surface would be noticeable. Plan B would be some Evaporust on paper towels.

    Michael
    I've done this to my cast iron table saw 3 or 4 times now with moving and it getting wet/ weathered. It has done no harm at all and cleans it up great.
    If it was a milling machine table that's a different matter, but wood working machines it's fine in my eyes.
    Using Tapatalk

  13. #13
    BobL is online now Member: Blue and white apron brigade
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    Default

    Some corrections


    Mechanical abrasion
    sander
    scouring ball
    wire brush
    Scotchbrite wheels - I love these, less damage than any of the above

    Reducing agent

    electrolysis

    Chelation
    Evapo-rust - I think it has EDTA in it.
    molasses
    citric
    acetic
    oxalic
    phosphoric - depends on strength

    Rust Conversion

    Tannic acid
    phosphoric - depends on strength

    Rust dissolution
    Strong acids like HCl and sulphuric

  14. #14
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    Default

    thanks for cleaning that up Bob

  15. #15
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    Port Sorell, Tasmania
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    Default

    I've cleaned up a few woodworking machine tables and my technique is to use a razor blade scraper first. This will remove the majority of the rust, follow up with a scotch brite pad using wd40 as a lubricant then wipe down. Keep the razor blade at a lowish angle to the table as you would using it on any other surface and it wont scratch, use short pushing strokes, you soon get the feel for it. Where there is a bit of pitting I have used a random orbital sander with 240 or 320 grit. It takes a lot of effort to remove any measurable quantity metal off a flat surface like a cast iron table, that is to remove light pitting.

    Be aware that some of the chemical rust converters can stain cast iron so it would pay to try a small area if that concerns you.

    Tony

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