VERY delicate rust removal

[beeza650Participant @beeza650]

I’ve used pretty concentrated phosphoric acid to remove rust – it keeps on going and eats the steel plus the phosphate coating is pretty nasty. I’ve used citric acid and am a big big fan – cheap in powdered form, the black residue comes off easily enough, it’s not too aggressive. I also use hydrochloric (brick) acid when I want something that’s going to go straight to paint…

but…what should I do with this (and a 50 odd other similar pieces) – what’s going to let me get that rust off without making a mess of the whole thing? Electrolysis?

Advice (ideally proven) much appreciated. Thanks 

[OldironParticipant @oldiron]

Whatever you soak it in will discolour it badly. I would be inclined to use mechanical means ie a fine brass brush and a white dish scourer very gently a good soaking with WD40 or similar for a few hours will help.  Its surprising how easy most of it will come off.

[Phil PParticipant @philp]

I use a product called “Evaporust”, it works very well on such things as musical box combs where you dont want to affect the steel too much.

Phil P

[Nigel Graham 2Participant @nigelgraham2]

I think you’ll have to accept a lot of steel has returned to Nature there. It looks as if it’s either been lying in a puddle or in contact with something that has attacked the steel electrolytically.

With the instrument dismantled completely and the threads protected (plastic sleeve?) I think careful wire brushing first to clear the worst, then degrease and pickle.

I’d go for the citric acid to be fairly gentle. Then careful work with ‘Scotchbrite’, one of those rubber abrasive blocks or ‘Brillo’ pad.

May be best to work on the least damaged / least critical areas first to establish the effects. The difficult bit is going to be protecting the internal threads.

[VicParticipant @vic]

Electrolysis for me. I’ve used it many times and it doesn’t etch the surface like acids.

[peak4Participant @peak4]

Evaporust, mentioned earlier, works well for me on measuring stuff such as vernier calipers etc.
Do gently wire brush off any loose rust before starting, as well as a thorough de-grease; I normally use the very fine stainless steel or brass brushes that come from cheap discount stores.
After treatment, soak/wash in very hot water, dry, and immediately spray it with something.
The hot water, is just so it dries quicker after wiping down.
I use Motorex 645 Protect & Shine; I still have old stock, but I think this is the latest version
https://motorex.com/en-us/moto-protect-spray–28154

See also, though I’ve not tried it myself (yet)

Bill

[Vic]

On Vic Said:

Electrolysis for me. I’ve used it many times and it doesn’t etch the surface like acids.

Thats what i am thinking. Does it take the black out of the graduation markings too?

[DellParticipant @dell]

I restore antique torsion clocks and use Evaporust but a word a word of caution don’t leave it in for more that 10 hours otherwise it will turn black although if it does it is easy to clean  off.

[Robert Atkinson 2Participant @robertatkinson2]

++1 for Evaporust. It chelates the rust causing no damage to the underlying steel. It’s water based so you do have to remove any oil or grease (solvent followed by hot water and detergent) before putting it in th Evaporust. On removal rinse with hot water and spray with WD-40 or similar or the very clean steel will start to rust again.

Robert

[beeza650]

On beeza650 Said:

On Vic Said:

Electrolysis for me. I’ve used it many times and it doesn’t etch the surface like acids.

Thats what i am thinking. Does it take the black out of the graduation markings too?

It will remove loose paint, at least that’s been my experience, so you could loose it in the markings.

[Phil PParticipant @philp]

And if you want a product to prevent corrosion, I find this is good stuff.

Atom-Mac

I use it on my motorbike and it works very well, and is very easy to apply.

Phil P

[jimmy bParticipant @jimmyb]

I had good results with evaporust followed by an hour in my ultrasonic tank.

 

Once metal has been eaten away by rust, it can be a lost cause.

 

Jimb

[parovozParticipant @parovoz]

Another way is by careful mechanical removal means. Where the faces are not dimension critical for the measurement where even extra caution is required.

So the process wound be.

For the base of the frame, a dead smooth single cut file, placed flat on the face and gently rubbed over the rust to ‘shave’ off the top layer without ‘cutting’ metal. Next, ultra fine wet and dry lubricated with WD40 or the like, supported by the file, again rubbed with the grain ( previous grinding direction ) to clean up. That in most cases will remove the rust without adversely affecting the surface.

Never do this by hand, ALWAYS support wet and dry with the file to maintain flatness and eliminate the risk of rounding or damaging the sharp edges. That’s the difference between bodge and care…..

Same approach for the barrel…

For the knurling…..

Grind a hand graver tool to match the ‘V’ of the knurling and gently ‘re-cut’ the knurling by hand to clean out the rust. Finish with a soft brass wire brush and WD 40 to clean and a hard bristle brush at the end to remove any brass residue.

That’s my ‘old skool’ means of de-rusting and I have done many concours level restorations in that way to very good effect, with care a near new appearance can be produced in many cases.

But the caveat is, that if the rust pitting is deep, it’s never going to loose the little black spots as they are too far under the original surface to be removed by such gentle means.

 

All the best….

 

[jimmy b]

On jimmy b Said:

I had good results with evaporust followed by an hour in my ultrasonic tank.

 

Once metal has been eaten away by rust, it can be a lost cause.

 

Jimb

I’ve got an ultrasonic cleaner – what was that needed for, to clean off the Evaporust residue?

That Evaoprust stuff isn’t cheap is it. Hope it keeps as it’s a lot cheaper per litre to get 5 but I’ won’t use all that in this round of cleanup.

[VicParticipant @vic]

Electrolysis V Evapo-Rust.

https://youtu.be/8dtDLQHjHBc

[ryan.carter848Participant @ryan-carter848]

That DIY solution works as well or maybe better (longer) than Evaporust. Definitely legit much cheaper too, used it multiple times now.

[beeza650]

On beeza650 Said:

On jimmy b Said:

I had good results with evaporust followed by an hour in my ultrasonic tank.

 

Once metal has been eaten away by rust, it can be a lost cause.

 

Jimb

I’ve got an ultrasonic cleaner – what was that needed for, to clean off the Evaporust residue?

That Evaoprust stuff isn’t cheap is it. Hope it keeps as it’s a lot cheaper per litre to get 5 but I’ won’t use all that in this round of cleanup.

I was getting rid of light rust on a joblot of screw tread gauges. They were left with a bit of dark tinge. An hour in the ultrasonic tank managed to leave the gauges looking good.

 

Jimb

[Mark RandParticipant @markrand96270]

If you have a large part to de-rust, molasses (as used for silage and horse feed sweetener) will work as well as Evaporust but at a far lower cost if you’re looking at multiple gallons. Electrolysis works well for large or small parts.

[beeza650]

On beeza650 Said:

<SNIP>

I’ve got an ultrasonic cleaner – what was that needed for, to clean off the Evaporust residue?

That Evaoprust stuff isn’t cheap is it. Hope it keeps as it’s a lot cheaper per litre to get 5 but I’ won’t use all that in this round of cleanup.

Not only does it keep well, it is reuseable. I keep used fluid in a separate container. I actually filter it but that is probably a bit OTT.

[bernard towersParticipant @bernardtowers37738]

I filter mine as well Robert you get an idea how well its working.

[Vic]

On Vic Said:

Electrolysis V Evapo-Rust.

https://youtu.be/8dtDLQHjHBc

Interesting one that.

The wrench is a bit of a read herring as it is different materials and not  put into the Evaporust. I’ve ignored the wrench.
On the studs and nuts the Evaporust appears to have caused less damage to the fine deails of the threads ans knurl / spline.

They also don’t seem to have agitated the Evaporust at all. Doing this speeds up it’s action considerably.

[SillyOldDufferModerator @sillyoldduffer]

The various methods have pros and cons, so which is best varies with circumstances.

Rust is mainly two different Oxides of Iron, both created when Iron and Oxygen react chemically with air.  The reaction is accelerated by damp, salt, Carbon Dioxide and other pollutants.  Not all rusted objects behave in the same way, so it may be necessary to try different approaches for best results.  Red rust expands and is flaky, black rust is solid and unsightly.

Phosphoric acid reacts with both types, converting them into Phosphates.   The result can be left in place as a nasty looking black mass, but that’s useful when holes are to be avoided.  So this method is good for sheet metal and iron work repairs when holes are unwanted, and paint and putty cover up.

Citric Acid is weak, slow acting, pricey and user-friendly.  Easy to clean with water.  It dissolves the rust taking the owner back to bare metal, and the acid penetrates below the surface.   Good for light clean ups of smallish parts rather than garden gates!  Leaves holes though.

Hydrochloric Acid behaves like Citric Acid except it’s stronger, faster acting and cheap.  Disadvantages are the need for rubber gloves and eye-protection, plus Chloride ions are left inside micro-cracks in the metal.  After about 5 years these detach paint, powder coatings and electroplate causing their protection to fail early.   May not matter, but when the finish must last a long time, avoid Hydrochloric Acid.

Sulphuric Acid is cheap and fast and there are no Chloride ions.  Much used by industry, but not easily obtained in  for hobby use.  Don’t expect top quality results from Drain Cleaner because the Sulphuric Acid in it is impure.

Chelating agents put a chemical cage around rust molecules causing them to fall off the rusty body.   Often found in proprietary mixes containing chemicals not otherwise available to hobbyists.  Good, but pricey, and better at some jobs than others.

Physical rust removal gets back to a clean surface quickly and unlike chemicals no waiting for a slow reaction to complete.  And chemicals struggle to get past existing paint, grease and dirt.   Unfortunately, physical methods don’t remove subsurface rusting, which is liable to cause trouble years later, typically by lifting paint off from underneath.

Electrolysis is probably the best single method, other than needing a bath and power source.  The chemicals are cheap and available.  Electricity speeds the chemistry up and the electrolyte penetrates deep into the metal.  Fast and effective, able to do both large and small objects.

Very common to find different methods being applied one after the other.  For example, when using Citric Acid, it pays to remove as much loose rust and dirt as possible before soaking in acid.   Likewise, to wire-brush garden gates before applying Phosphoric Acid.

They all work, but it pays to match the answer to your particular problem.  If one doesn’t work well, try another.

What’s done next is also important because newly de-rusted objects start rusting immediately.  Paint and electroplating both have to be done quickly.  Or apply oil or lanolin pronto.

Dave

 

 

 

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