OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Paint and Decals Rust and Corrosion - Removal Options ?

G'day Widget, I've thought about using an old 44 as well because it would give an even current flow to cover the job being cleaned but remember how the sacrificial anode dissolves? You'll come out to find half your drum gone and your treasures on the ground.
When using electrolysis it apparently releases the hydrogen from the water which causes hydrogen embrittlement in the metal. This is a mayor problem in things that take load like gears and shafts. Apparently there are two ways to dissipate this hydrogen. The first is to leave it alone and it will come out over time and the other is to bake it in the oven. Please note I say apparently a lot as I've only done this a couple of times and my knowledge comes mostly from doctor google.
I have never tried the vinegar trick but have read of it a few times. Does that elcheapo vinegar do the trick?
From my understanding molasses is sensational and can be used mixed down with water but has three shortfalls. One is it takes longer. Two is the cost of molasses, even from a stock feeder and thirdly while molasses does dissolve rust first it will also dissolve good metal whereas electrolysis will only dissolve rust and then stop no matter how long your piece is left in the bath.

Thanks for the info Slash

With vinegar, just the cheap homebrand stuff is all I use. Threw smaller stuff (nuts n bolts etc..) into a jam jar, filled with Vinegar and left it on the shelf. All the rust and crap shows up on the surface .

Yep. It is slow [days to weeks, depending on thickness of rust], so you have to be patient. It will corrode sheetmetal parts if left in too long, too. And it does get pretty stinky.

It really has to be mixed with water. Anywhere from about 1+7 to 1+10 molasses:water ratio will work well.
Tip: Use hot tap water when mixing it up - speeds things up. A 5kg bucket of black molasses was about $13 from the local stock supplies joint, last time I bought some.

Soda Ash is also available in bigger packs from swimming pool chemical suppliers, and that works out cheaper than bicarb soda [aka Sodium Hydrogen Carbonate]. I would not use any chloride-containing electrolyte solution, like salt water - the metal absorbs some of it, and perpetual after-rust problems are likely.

For mechanical rust removal, a 'twist knot cup type' wire brush on a 4" angle grinder is about the best method I've used. As freebird mentions, good PPE is essential - eye protection [preferably full face shield], long welders' gloves and a leather apron. The flung off bristles will penetrate normal clothing.

Rapid after-rusting is a problem with any of the chemical [including electrolytic] de-rusting methods.

One of the best ways to passivate the surface is to rinse it off thoroughly, and swab it with diluted Phosphoric Acid solution before it dries. This will form a thin protective grey coloured Iron Phosphate surface coating, which is also a good base for the primer coat. Nearly all of the commercial 'rust remover' products are Phosphoric Acid based - if it doesn't show on the label, the MSDS will say. Try a dilution of about 1+4 to start with; if the metal surface doesn't turn grey pretty quickly, add a bit more rust remover.

For small steel parts, just boil them for 5 minutes or so in clean water to passivate them.

Thanks gadge :), just wondering, do you prefer getting straight Phosphoric acid and diluting if needed or do you recommend just getting a specific ready-to-use rust remover/converter?

Also, picked up a set of those twist knot angle grinder attachments, seemed to work quite well.. even on my finger :p .. took off a heap of rust from the blade plate.. primed it up, gonna give it a quick coat of black and chuck it back on the mower..

If you can get your hands on Concentrated [85%] Orthophosphoric Acid, dilute it at 1+9 ratio. That works for me. As always, add the acid to the water, not vice versa!

The rust removers are easier to get for most folk, hence my recommendation. The commercial rust removers also usually incorporate some sort of surfactant, to act as a degreaser for metal that isn't squeaky clean.

Yup, they're pretty aggressive at removing rust. Only thing is, they won't clean all of the residual rust out of pits in the surface, unless the pits are shallow. My procedure there is, to give the pitted areas the Phosphoric Acid treatment before painting. If appearance matters [as in the upper side of a mower deck], metal-filled epoxy such as Devcon or JB Weld can be used to fill the pits, after they've had the acid treatment.

Great! thanks Gadge, much appreciated

Quick question.. with Phosphoric acid, when it reacts with rust it creates a primed surface .. though with rust being scattered after cleaning, would you still apply a layer of epoxy to cover the areas that weren't primed by the PA ? (if u know what i mean)

Well, the phosphoric acid actually dissolves the rust, and it washes away with the rinse water - if it has been in contact long enough. That's why the commercial rust removers have a 'thickener' added, to give the acid time to do its job.

Scratching as much of the rust as you can out of the pits before applying the acid also helps, but it's a tedious job if there are a lot of them.

Those epoxy products are quite viscous, and very suitable for filling pits, but not as an overall coating. It's simpler just to swab the whole surface with the acid after doing the pitted areas - as soon as it turns grey, it's ready to rinse off, dry, and hit with a primer coat.

woops I think I meant to write primer .. not sure why I put epoxy.. maybe meant etch primer *shrug*



Thanks gadge :), where do you recommend getting the more concentrated Phosphoric Acid / Orthophosphoric Acid? I found this site which has a local store if its still there) http://kegking.com.au/cleaners-and-sanitising-equipment/pure-phosphoric-acid-96-pure-300ml.html .. not sure if it's thick like the one you mentioned though.



thanks for the info .. I think I meant to write etch/primer though lol

Thanks again

Well, that's cheap enough, but it's blindingly obvious that that mob have no clues about calculating acid concentrations.
Commercial 'syrupy' Orthophosphoric Acid is 85% H3PO4, and diluting that with 4% demin water sure doesn't get you to 96%!

Their packaging looks a bit suss for that product too, unless it has a back label with the hazard diamonds for Dangerous Goods Class 8, and other safety info on it.

The 'thickened acid' rust removers are sold at paint and hardware shops, as either 'rust removers' or 'rust converters'.

The other commercial 'rust converter' chemistry in use is Tannic Acid based, but this type is less common than phosphoric acid, and much more expensive these days.

I'll have to check out a some more hardware stores.. bunnings and SCA have the converters, but I think the % is only <50% Phosphoric Acid.

There's also sydney hardware.. but that's some distance from me.. they seem to have some.. various cleaning suppliers too around me ill have to call up.



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Here a clip of my Electrolysis setup, anyone have any suggestions on it, feel free to post

[video][/video]

PSU running @ 12v10A .. oddly enough, i tried 5V30A but it didnt seem effective.. almost as if nothing was happening *shrug*

Has anyone used...

Metal Rescue - pre-mixed about $50/5L @ REPCO, apparently re-usable

Evapo-rust - pre-mixed about $88/5L @ Supercheap (much more expensive than Metal Rescue).. or for Concentrate $100 (makes 6L) from the website. Also apparently re-usable

Rust Bucket by 'Action Corrosive', comes in 1L concentrate(makes 5L) - about $40. Unknown if re-usable.

Have read a few reviews of Metal Rescue and evapo-rust.. not much about Rust Bucket though.

Just wondering how they may compare to, say, using Acidic Rust Removers and Electrolysis ?
From the pics/videos, they seem to clean up nice.. and being water based, seems easier to clean? plus I 'think' I read they don't flash-rust as easily as other methods??



Thoughts?

G'day Widget,

Well, all I can say [as a field chemist with Baker Hughes in a past life, which included quite a lot of oilfield corrosion related work and training] is that there's far too much 'snake oil' in the blurbs for all of those products, for my liking.

And none of them have a readily downloadable MSDS available.

So for me, the bottom line is that they may well 'work like it says on the packet'. But their pricing is highly likely to be in the 'predatory' class, for what's actually in them...

What's everyone's thoughts about vinigar or coke? Not interested in connecting power supplies up etc I just want an easy old school method

G'day Tjames,

Well, it doesn't get any more old school than the Molasses/water bath described earlier in this thread, and also pictured in this one; https://www.outdoorking-forum.com.au/forum/u...-160cc-isolation-project.html#Post105218

Coke is just an exy way of buying the 'active ingredient', which is actually the Orthophosphoric Acid in it! The Food Additive No. is 338 for that stuff.

Thanks alot for that. I want to give it a go!
Got a camando that I want to restore

Yes I find the molasses bath a great thing, yesterday threw in the cutting disc off a Victa Cortina 2 at about lunchtime today pulled it out a gave it a pressure wash which really blasts the crud off and it is now back in overnight.
I would say lunchtime tomorrow another blast and it will be ready for a bit of a sand and I spray with Lanotec to stop the rust flash until I am ready to paint, when ready I wash off in the parts cleaner pressure wash wipe over with wax and grease remover before painting.

Beech

Yes Beech, I have had a similar result with it - just strips it right off. An older guy I know bought a few 44gal drums when a business closed in the 80s and soaked a tonne of parts in it before it became so saturated it lost effectiveness.

For any WA guys, Mirco Brothers of Neerabup and Bibra Lake have molassis by the kg for $1.6/kg. About the cheapest I have found over here so far.

BYO bottles or they also have a 15l pail with lid for $4.

Plus, if you want epsom salt for the lawn for spring, its $25 for 25kg. Tried to calculate the cost it would be at bunnings but typing 6.85/kg x 25 into the calculator made my eyes water too much haha