Removing rusted bolt stubs from aluminium

Adrian Harris · Post by **Adrian Harris** » Mon May 25, 2009 10:14 am

Has anyone ever utilised the trick of using an acid to remove the remnants of broken steel fasteners from aluminium ?

I'm rebuilding the Sherman prototype and due to its lengthy stay out in the Devon weather, several of the bolts in the sprockets have sheared off due to rust.

I've read about using Nitric or Sulphuric acid to erode the steel without affecting the aluminium but would be grateful to hear from anoyone who has actually used this process.

Adrian.

clive Lockwood · Post by **clive Lockwood** » Mon May 25, 2009 10:13 pm

if you can take the parts to a local engineering company a lot of them use a technique called spark erosion which will completely remove corroded metal from alloy threads with out any damage, worth a look through the yellow pages.

Derek Attree · Post by **Derek Attree** » Tue May 26, 2009 7:28 am

Adrian
I have used acid for this and it does attack the alloy as well
spark erosion is a better way to go.
I have also drilled down the screw using a drill with the core size of the thread, eg on a 3mm screw drill 2.5.

Hope this helps

Derek

Allan Richards · Post by **Allan Richards** » Tue May 26, 2009 12:52 pm

Adrian,

If you can still get hold of the stub of the bolts to turn them try heat first. Aluminium expands more than steel and it will break the rusting. Obviously be careful not to melt the aluminium.

Fredrik Jorgensen · Post by **Fredrik Jorgensen** » Tue May 26, 2009 2:18 pm

I use that way to Allan, thou i first use soapwater

on them and it tends to get into the threads it seems.
I got the tip from a old auto mechanic "soak it with a spraycan and let it set, try loosen it after ca 30 mins.If the bolt mooves just apply more soap/water solution and twist it back and forward. If the bolt is really stuck, apply heat with a heat gun or propane.
It usually work great for me i must say.

Regards
Freddie

Brian Leach · Post by **Brian Leach** » Wed May 27, 2009 10:05 am

Hi,

I work on Merchant ships and have this problen constantly.

I very strongly recomend PC Blaster. It seems the best out there. I would try this before heat, adif, or the electric stuff.

Good Luck,
-Brian

Martin Cohen · Post by **Martin Cohen** » Thu May 28, 2009 4:26 am

Hi Brian,

can you be more specific about the product? Where is it found, maybe some info about it on line for example?

I've found saturating a bolt with a thread solvent spray, or soap helps. Differential heating may help by applying ice to one part while carefully heating another for example. Sometimes a mild tap while doing the above helps to free a part.

Cheers all,

Adrian Harris · Post by **Adrian Harris** » Thu May 28, 2009 9:30 pm

Thanks for all the comments and suggestions

I've been away this week but have received a quote from one of the companies I contacted about spark erosion. The inital price was Â£20 per bolt

but due to the quantity they have said they may be able to do it based on an hourly rate instead, so I'll need to audit how many I need to remove and then take it from there.

I tried Googling "PC Blaster" but got everything from computer speakers to ways to improve my (non-existant) six pack

Nothing about rust removal though

<later>

Did you mean "PB Blaster"

That gets a few useful looking hits...

Adrian.

Martin Cohen · Post by **Martin Cohen** » Tue Jun 02, 2009 12:34 am

Thanks Adrian!

Now I see it is "PB Blaster"