Alum& PVD coating

[Nucejoe]

Hi all,   

Have a PVD coated winding crown with stem broken in it, wonder if alum destroys the PVD coating?

Its yellow gold tone PVD. 

TIA

Joe

 

 

 

[Tudor]

What brand watch?

Seiko pioneered the TiN coating, which is gold colored, and now used on cutting tools to improve their life. 
 

You need to determine if it’s gold, or another coating, and then determine if that coating is effected by Alum. 
 

No way anyone here can answer well with the little information given. 

[Nucejoe]

Its just a Swiss candino $150 quatrz watch so no gold I suppose.

Would a picture help.

How do you determine what material or if affected by alum, that is the question.

[Tudor]

Hmmm... Besides the coating, we don't really know what the crown itself is made of either.

In you position, I'd source a generic "gold" crown for it, and either run with that, or wait until that is in hand before experimenting with the original crown.

Is it a screw-down crown, with a spring loaded "clutch" mechanism inside, or just a tapped solid? If it is a complex assembly, it might not be a good idea to introduce chemicals that could effect the other components of the assembly.

I think if you used an oiler, to place the solution precisely, you might be OK working on a solid. But, I'd still want a "fall back" plan on hand, in case things went wrong.

I have seen Burgeon has a dissolving solution, but I know nothing about it beyond it's existence. It's pre-mixed and probably far over-priced, but might be worth looking into.

[AndyHull]

1 hour ago, Nucejoe said:

Its just a Swiss candino $150 quatrz watch so no gold I suppose.

Would a picture help.

How do you determine what material or if affected by alum, that is the question.

Sadly the only obvious way to see if it is affected is to try it.

If you think it might only affect the finish, you could try potting the item in wax, with just the broken stem exposed, but if the main material that the crown is made of does dissolve in alum, then it will go the way of the dodo no matter how careful you are.

I presume there is not enough exposed thread to catch with a pin vice or grip with wire cutter jaws. 

Maybe drilling the broken stem out is the best way forward, you could also try a reverse pitch drill bit, or even simply running a normal drill bit backwards (carefully and slowly, as it will chatter and possibly shatter). The idea is to catch the broken threaded item with the bit and unscrew it with the drill.

You will need everything clamped down in your drill press vice though, otherwise your results will be pretty hit or miss. Trying to drill it out by hand is a non starter, and an almost guaranteed way to drill a hole in your hand. Don't ask me why I know. 

Edited September 23, 2020 by AndyHull

[Nucejoe]

Its a signed crown and taking a bath in alum right now.

 I do have good quality genuine Swiss gold plated crown fhat would fit, unsigned though.

Will let you know if it like the bath or not by your evening time. 

Best

joe

 

 

[Tudor]

Fingers crossed for your success!

[AndyHull]

I think alum probably wont react with aluminium, due to aluminium's protective oxide coating, but I may of course be wrong. It may however react with other metals that are more reactive than iron. Does anybody know what the chemistry is that causes alum to eat steel? 

[Marc]

According to Wikipedia, alum (potassium aluminium sulphate) does not affect aluminium. 

[Nucejoe]

Alum worked with no damage to the coating.

 Someone may recognise what this coaing is by the picture.

Took alum several days though to dislove the stem.

Hope this helps.