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2nd April 2013, 12:32 AM #1GOLD MEMBER
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Removing rust with Citric Acid - test results
This is a follow on from FenceFurnitures original post here.
hi FenceFurniture, thought you might be interested in my test results using two sources of citric acid on a very rusty bar for 5 hours
Attached are some pics of some citric acid powder in water on rust. I used two products to test, and both gave much the same result - cooking Citric Acid from the supermarket, $3 per 100 grams, and Concrete Etching from Bunnings - $2 per 100 gm.
Took just 5 hours, with a quick brush with a wire brush by hand every hour - amazing result too.
White Knight advise that their concrete etching powder is pure anhydrous citric acid. I used the same strength for each powder, 100 gm per litre of water.
I looked at EvapoRust too. It is made in Cairns and readily available online. The problem with Evapo-Rust is the cost - $25 per litre, or $75 for 5 litres, plus postage, but it is just as effective as the citric acid, but does not etch the clean bare metal, is non toxic and biodegradable - can be used as a hand wash too.
CA_01.jpg
Original rusted iron bar, wire brushed on RHS
CA_02.jpg
Test pieces cut from wire brushed section
CA_04.jpg
Test piece inserted in food CA
CA_05.jpgCA_05 (2).jpg
The recently cut metal is attacked very aggressively with the food CA
CA_06.jpg
Inserted in White Knight concrete etcher ( Citric Acid)
CA_07.jpg
Results after the first hour
CA_08.jpg
Results after 4 hours - food CA
CA_09.jpg
Results after 4 hours - concrete etching CA
CA_10.jpgCA_11.jpg
Finished product after 5 hours and a quick wire brush by hand.regards,
Dengy
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2nd April 2013 12:32 AM # ADSGoogle Adsense Advertisement
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2nd April 2013, 08:16 AM #2
Good work Dengy. Five hours seems a long time - were you doing it at room temp (although that's a little elevated in your neck of the woods)? I usually do it at about 70 deg. That seems to be enough for one cycle, then give it a nuke in the microwave for the next lot (yeah, I'm a scab, even with my $5 per 500 grams bulk CA ).
Also, I noticed that your solution didn't turn green as mine habitually does.
For heavily rusted pieces I often take them out after a little while and give them a brush to get rid of the new loosened layer - seems to accelerate things.
You should see how CA cleans up Carbide - stunning! Maybe not a great idea to soak router bits in it - just use a plastic brush. BobL has a concern about the CA possibly weakening the glue between the carbide and the steel.
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2nd April 2013, 08:27 AM #3GOLD MEMBER
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Hi FF, I started out with boiling hot water, and then it cooled down gradually over the next hour or so. I took the pieces out every hour and wire brushed them by hand to remove the oxides formed and expose the next layer of rust.
I used electrolysis ages ago on an old rusted 10" saw blade with TCT teeth, it works perfectly, no apparent affect on the teeth, still cutting strongly even after a couple of sharpenings at the local tool shopregards,
Dengy
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2nd April 2013, 09:03 AM #4
Right, just very heavy rust then.
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2nd April 2013, 10:15 AM #5GOLD MEMBER
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Right, just very heavy rust then.
regards,
Dengy
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2nd April 2013, 05:30 PM #6GOLD MEMBER
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Great stuff, thanks for posting Dengy, I've got a few things that need rust removal. Might go in this direction.
-Scott
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2nd April 2013, 07:39 PM #7
If you want quick (like 15-30 minutes) rust removal, you really can't go past hydrochloric acid.
A note for any users of any acid based rust removal - if the part is high carbon steel (springs or chisels or anything over about 30Rc), it's a good idea to bake it in the oven (200 degrees C for four hours) immediately after rinsing off the acid to avoid hydrogen embrittlement. (maybe pop it on the shelf below the Sunday roast to stop it getting all rosemary and garlic smelling...) Time will also (apparently) cure hydrogen embrittlement, but we are talking 6-12 months.
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