Cleaning scale from Enigma rotors

[amiklic1]

The time has come to spend some time on my Enigma rotors, not to make them look better but just to preserve further degradation.

These rotors were saved from an U-boat which was laying at the sea bottom for decades, and they are in nice state, considering that fact.

Amongst 5 rotors I have are rotors no. VI and VIII, extremely rare naval rotors.
I intend to pay special attention to all details, and I am pretty sure this battle is going to last for months before I finish it.

I have enough experience in fine mechanics and electric/electronics, so dissasembling these babies will not be a problem after I remove scale and clean them a bit, to free the parts to move apart from each other.

What I am worried about, and I am looking for a help in that, is the best/most efficient way of dissolving the scale which has formed over the rotors and which has already degraded large portion of them.

It is a kind of yellowish-brownish scale, and looks/feels just like limescale but is a kind of softer and brakes to powder when lightly scratched. The main problem is that it has also formed on un-acessible places, so dissolving is the only way to go, I am afraid.

I was thinking about vinegar, citric acid and days/week of dissolving, but I'd like more experienced to say a final word.

Here are the photos, not too good but it's visible where the problem is, every and all advices welcome.

[amiklic1]

No replies...

In the meantime, it's been put in citric acid solution, and I am closely watching the scale dissolving, bubble by bubble.

I plan to keep it in it for an hour, take it out, wash with fresh water and repeat the process if nothing goes wrong.

I was using citric acid on helmets before, keeping them for a week or two, and that removed all the rust.

As this is really more gentle than an old rusty helmet, I'll keep an eye all of the time. I do not want to loose those nice rotors.

[Paul R.]

If you do not want to soak your item in an acid solution. I would recommend using a hand tool like a dermal tool (or one like it). I would use the soft nylon round bristle brush to clean off the residue. They also have a few other assorted brushing or polishing pieces. <O</O

[amiklic1]

Hi,

thanks for the reply.

In fact, it's almost done, already.

I have done like this:

1. soaking in citric acid solution, for 1 hour, than washing with fresh water, than soaking for another hour. That helped by dissolving some residue (thin layers), but not with the thick ones.

2. Cleaning the rotors with a mid-soft hand brush under water. That helped to clean the metal parts which were dirty after acid acting. It was much nicer after this step. Not cleaned, but most of the dirt removed.

3. Usinf Proxon 20.000 rpm tool and a micro mill (0,5 mm) i succeded to remove all residue with no parts damage. The point is in very slow moving and in high speed, so the residue parts were just flying-off the rotors. I also suceeded to get into the aluminum crowns at places where it is divided to 2 sides, so to clean internal parts and prevent any further degradation. In that step, direct light is a mst, to be able to see what's inside and not to damage healthy material.

Now I am planning to do a display, with 4 rotors displayed as thea came, only cleaned, and the worst one will be in exploded view on a shaft, just I saw in some museums.

So, the issue I thought will last for weeks is being finished in hours. I decided not to take the rotors apart fully in this stage, even if that means possible further material degradation from within the rotors themselves. I'll leave that to some other time, when I'll have better idea and a bit more time.

I'll post photos after I finish with this.

[August]

I just now came across this thread - please post you photos ! I'm very interested in your work and results. If you have before and after photos that would be great. Thanks -