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Thread: Best Way To Clean Rusted Surface
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2nd Aug 2018, 06:31 PM #1Golden Member
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Best Way To Clean Rusted Surface
G'day
I've begun cleaning up the second hand Hafco AL330A I recently purchased and could use some advise on cleaning up the bare metal surfaces.
I had a good go at it with a fine grade steel wool, oil and turps but didn't get the result I was after, it was good on the ground/scraped surfaces but I want to try and get a nice finish on the other bare metal parts.
Would you advise I move to a courser steel wool, like triple zero or double zero?
DSC_3346.jpgDSC_3347.jpg
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2nd Aug 2018, 06:44 PM #2
Hi Nedshead,
You might try wadded aluminum foil and light oil - 3 in one.
The technique works for me in cleaning rust from carbon steel pocket knives I have acquired for my pocket
knife collection.
It removes the rust but will leave the pits.
I have not tried it on a lathe or any other cast iron for that matter.
Grahame
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2nd Aug 2018, 07:34 PM #3Banned
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Everyone will frown at this but I use either a scotch brite or a wire brush. It would probably wear the surface if you used them all the time, but removing rust from a lathe is not something you do everyday.
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2nd Aug 2018, 09:14 PM #4Member: Blue and white apron brigade
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I assume you mean in an angle grinder?
And by wire brush I don't mean those HD twisted knot type wire strands but long straight (or slightly crinkled) thin strands, some which break off an are like fine needles flying through the air so full PPE is needed
If it's not a MW reference surface I do the same - sounds rough but its damn fast.
On ww machinery I do this even on reference surfaces.
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2nd Aug 2018, 10:39 PM #5Novice
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I use white vinegar to clean up rusted tools. Some have been severely corroded and have come working again. I soak them for a day and clean up with a wire brush. The rust just falls away.
Soaking a lathe overnight might be a problem though. Perhaps paper towel or cloth soaked in vinegar would work or just vinegar and a wire brush as it doesn't look severe. Soap or washing soda will get rid of any acid left if that is a problem
Another thought for cleaning rust. Coco Cola works too. The real stuff. Or rust converter. Coco Cola is rust converter with added sugar.
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3rd Aug 2018, 01:35 AM #6China
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green scotch brite + wd 40 or Inox
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3rd Aug 2018, 08:35 AM #7Golden Member
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+1 China. I keep my old bits of tired green scotchbrite for such things. New pads are pretty abrasive but older is much friendlier. Some wd40 and rags to stop the oil getting to places you don't want.
Greg.
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3rd Aug 2018, 11:06 AM #8Senior Member
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This is a tricky one. It's not a precision surface ie. not the bed, but it's not going to be painted and is highly visible so you don't want to change or abrade the surface significantly. And those oil fittings are problematic.
I assume that you are not going to strip the machine down, so soaking in vinegar is not an option. If you swab vinegar on the surface it will run down into other parts of the machine below, and since you can't get in there to rinse and neutralise the vinegar that would not be a good thing.
Wire brushing by machine or hand will damage the surface and round off the bolt counterbores and those still crisp chamfered arrises, damage the adjacent paint and also damage the oil fittings, so I would not do that.
I think your best bet is to use scotchbrite soaked in rust converter (any phosphoric acid based product), but you'll need to thoroughly degrease and rinse off any oil or turps left from the previous operations so that the rust converter can get down in the deeper rust damaged areas. The advantage of using rust converter is that it does not need to be rinsed off or neutralised, plus it will leave the converted rust in the bottom of the low spots which actually is a good surface to hold oil which will prevent moisture from getting down there in the future.
My personal preference is for the final strokes of the scotchbrite rubbing to be in one direction, to get rid of the otherwise random swirly pattern. After rubbing the rust converter in and getting the top surface to where you are happy, leave it for 10 to 15 minutes, then wipe off the residue with some sort of thinners or turps, then immediately apply oil to stop flash rust from appearing. The aim is to keep the parts of the original surface that are rust-free as shiny bare metal but leave the converted rust in the rusted pits.
My guess is that both those examples in the photos will clean up nicely, and the result will be an even shiny surface that won't look too different from when it was new. After all, even new cast iron is not exactly like polished stainless steel.
Hope this helps, and whatever method you use please take "after" photos when you are done.
Graham.
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3rd Aug 2018, 12:21 PM #9Member: Blue and white apron brigade
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Most folks are not aware that Phosphoric acid (PA) is a stronger acid acid than vinegar
As an example the pH of common vinegar (5% acetic acid) is around 2.
To have a pH of 2 the PA would have to be 5x more dilute ie 1% and most rust converters are in the 10 to 40% range with some industrials reaching 75%.
PA doesn't just act on the rust and it will attack raw steel if left for too long which means if it gets down into any grooves and crevices it will make a mess.
Most rust converters also contain detergents which forms a scummy layer and it has to be removed.
The surface left behind by applying PA to stock blued steel is shown on the top strip RHS and on bright steel on the bottom strong (also RHS)
BtW the RHS is tannic acid of a similar pH - it leaves a much smoother surface.
ClearMetal.jpg
Brushing with a light/soft wire brush will only round off steel edges if the wheel is driven hard the wrong way towards the edges.
If the rotation and stroke direction are right it wont make any difference in this application.
It wont damage the brass unless the wire wheel is pushed and and those ares could be skirted around and finished by hand.
I have used these light wire wheels on CI and steel surfaces with original milling marks on them and these wheels have barely touched the milling marks indicating that they are not as aggressive as they appear.
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3rd Aug 2018, 08:13 PM #10Golden Member
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Thanks for all the suggestions,
I was shying away from using scotch brite pads because the last time I used it to clean the top of a cross slide it left deep scratches, but today I found a drill mount red scotch brite wheel in super cheap (not my usual hangout) that felt pretty good so I gave it a go.
DSC_3351.jpgDSC_3348.jpgDSC_3352.jpg
Can't complain with the results, it knocked the rust down and left a good finish.
Cheers
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4th Aug 2018, 09:25 AM #11Golden Member
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I have some of those too. For $5 each or so they are gold. )
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5th Aug 2018, 10:08 PM #12Golden Member
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These scotch brite wheels are great, don't know how I lived without them, I should have everything cleaned up in no time
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