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17th May 2017, 11:59 am | #1 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
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Alternative to Alum to dissolve rusty steel
I am trying to remove the remains of a very rusted in threaded steel rod from a blind hole in a brass end cap. I am using Alum and it is both slow and does not attack the rust, only clean steel exposed when I drilled out as much as I dare.
Has anyone had success with other chemical methods? |
17th May 2017, 12:47 pm | #2 |
Nonode
Join Date: May 2007
Location: Preston, Lancashire, UK.
Posts: 2,511
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Re: Alternative to Alum to dissolve rusty steel
Is there any sort of electrolytic method you could use?
Andy |
17th May 2017, 3:33 pm | #3 |
Nonode
Join Date: May 2007
Location: Preston, Lancashire, UK.
Posts: 2,511
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Re: Alternative to Alum to dissolve rusty steel
Will that not dissolve the brass as well?
Andy |
17th May 2017, 3:46 pm | #4 |
Heptode
Join Date: May 2014
Location: Salisbury, Wiltshire, UK.
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Re: Alternative to Alum to dissolve rusty steel
Ive used Fertan rust treatment. Might be worth a try
D |
17th May 2017, 8:33 pm | #5 |
Rest in Peace
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Re: Alternative to Alum to dissolve rusty steel
Phosphoric acid is used to attack rust. Dilute acid is called Coca Cola. Jenolite is more concentrated but doesn't taste so good.
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17th May 2017, 9:06 pm | #6 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
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Re: Alternative to Alum to dissolve rusty steel
What diameter is the rod and the hole?
Professionals would use a spark-erosion machine https://en.wikipedia.org/wiki/Electr...tion_machining rather than trying to dissolve it (brass is tricky chemistry, being an alloy). I've had this technique used in the past to remove sheared-off steel studs from an aluminium alloy Jaguar engine-casting. Not cheap, but it works amazingly well. The other option is an "anticlockwise drill bit" - for example http://www.phantomdrills.co.uk/shop/...and_drill_bits to drill down into the steel screw. The combination of heat from the drilling, and the unscrewing-torque as the drill-bit bites into the steel, coupled with the fact that once there's a hole through the steel it will 'relax' slightly from its grip in the thread - often the broken-off screw/stud will unscrew itself when you've only drilled a short way into it! |
17th May 2017, 9:08 pm | #7 |
Octode
Join Date: Jan 2012
Location: Wimbledon, London, UK.
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Re: Alternative to Alum to dissolve rusty steel
Evapo-Rust worked pretty well on really rusty tools that suffered in a flood. I purchased mine from here:
http://www.frost.co.uk/evapo-rust-su...-us-quart.html It might be worth a try on your task, but even if it isn't quite doing what you want, it is still worthwhile having some of this stuff in the workshop. No connection, just a satisfied customer. Colin. |
17th May 2017, 9:17 pm | #8 | |
Octode
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Re: Alternative to Alum to dissolve rusty steel
Quote:
As it happens, there are several liquids called "phosphoric acid". They are chemically related, but any more on this would be both off-topic and boring to everyone else. Colin. |
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17th May 2017, 10:31 pm | #9 |
Rest in Peace
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Re: Alternative to Alum to dissolve rusty steel
Oxalic acid was used to remove cast iron brake dust from trains. I believe it is quite toxic and had to be used with care.
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17th May 2017, 10:45 pm | #10 |
Dekatron
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
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Re: Alternative to Alum to dissolve rusty steel
Have you tried heating it? Brass has a coefficient of linear expansion about 1.5 times greater than steel, so the steel should become looser the hotter it gets. I haven't had to try it with Brass/steel, but Brass has a coefficient of expansion only slightly less than Aluminium, and when I had to replace an aluminium piston in my car engine, it had to be heated to about 200 deg C in an oil bath to allow the steel gudgeon pin to be removed. At that temperature it just fell out, whereas at room temperature it was absolutely immovable.
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18th May 2017, 1:17 am | #11 |
Dekatron
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Re: Alternative to Alum to dissolve rusty steel
I would have guessed that any chemical that would attack the steel would very likley take the zinc out of the brass, if not the copper too.
Phosphoric acid reacts to form an inhibiting layer of phosphate on steel, so that will not work well. I tend to go with Tanuki on this; spark erosion or mechanical methods. B
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18th May 2017, 7:22 pm | #12 | |
Octode
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Re: Alternative to Alum to dissolve rusty steel
Quote:
I wouldn't recommend anyone who isn't knowledgeable to use oxalic acid because of the toxicity factor, but it is good at removing rust stains from baths, sinks, etc.. (I am a trained research chemist). Colin. |
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18th May 2017, 7:30 pm | #13 |
Banned
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Re: Alternative to Alum to dissolve rusty steel
Oxalic acid is the active ingredient in Bar Keepers Friend cleaning powder.
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18th May 2017, 8:13 pm | #14 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
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Re: Alternative to Alum to dissolve rusty steel
Alum is used by clock restorers so is pretty safe with brass. It's even used with aluminium. The threaded shaft is about 7mm diameter and it had completely rusted through at the entry point to the brass end cap!
I have ordered some oxalic acid primarily to try to remove some stains from a piece of dilapidated antique furniture but I will try it on this. Meanwhile I have persisted with the Alum and am about 80% done but it leaves the rust residue in the thread which is difficult to scrape off. It's not helped by being a blind hole as the gases hold the liquid back. Alum has had no affect on brass but I am not sure how bakelite knobs would cope as it has been at boiling point for a few hours so far. Last edited by PJL; 18th May 2017 at 8:19 pm. |
18th May 2017, 9:00 pm | #15 |
Dekatron
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Re: Alternative to Alum to dissolve rusty steel
I use Viakal which is a domestic acid limescale remover on heavily corroded brass. It strips the oxides and verdigris very well and does not discolour the brass unless left for a long time. Whenever you clean brass this way, you have to follow up with conventional cleaning as it reveals the corrosion damage on the surface layer of the brass.
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18th May 2017, 10:14 pm | #16 |
Dekatron
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Re: Alternative to Alum to dissolve rusty steel
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18th May 2017, 11:36 pm | #17 | |
Nonode
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Re: Alternative to Alum to dissolve rusty steel
Quote:
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