Chamber construction...what about nickel plating?

[John Taylor]

I am new to all this and trying to build a first fusor. One of my hurdles is obviously a vacuum chamber. I have access to a large valve body made from mild steel. This would give me three large flanged connections into an approximately 12 inch spherical cavity where the innards of the valve used to be. If I electroplate the inside of this chamber with nickel and then bake off any trapped gases would this be a suitable substitute for the stainless chamber I would like to have but can't afford? If this has been addressed before, I appologize, but I couldn't seem to find any postings concerning this. Thanks in advance for any information.

[Richard Hull]

Mild steel ought to be OK ,as is, provided it is clean and the chamber kept under some sort of vacuum. Don't both to plate it.

Richard Hull

[John Taylor]

Thanks for the very quick reply! I love building projects and will keep this forum up to date on my progress, as I will use whatever I can find at as low a price as possible.

[Doug Coulter]

I do plating here quite often. I'll agree with Richard -- not worth it. If done right, it will cost you more than the SS chamber would have (assuming you can find a used one, no one really buys big SS tanks new here). The prep is the hard part...and you of course have to bake and clean, bake and clean first, else gas trapped behind the plating will make it bubble and come off.

Since I have the stuff, I did try this once, using an old CO2 cylinder as the chamber, then copper, then nickel.

It wasn't worth the effort. Clean mild steel does rust very quickly -- especially when exposed to atmosphere after it has cleaned up in a vacuum. So you'll have to keep it under vacuum. Otherwise, the resulting rust slowly disassociates under vacuum and acts like a slow leak for what seems like forever.

Of course, once you have a good vacuum (which is going to cost more than the tank anyway) you can evaporate any of a number of things -- Al and Ti come to mind here -- and get the same effect in a few seconds and with a lot less work!

[DaveC]

To Doug's comment about Al and Ti, evaporating, I can add that SS also evaporates and plates very nicely. The temperatures are very close to those needed for Ti.

The issues for the bare steel chamber are fairly simple..... when you are in glow discharge mode, anything with more than a trace of oxygen will go after the steel surface.... But since the fusor work involves D2 fill and preferably vanishingly low levels of oxygen, (for best results), the steel should do reasonably well, once the chamber is pumped down.

To be able to evaporate any metals with good results, you will need to reach pressures in the -5's (Torr) or below, for a nice clean deposition.

Dave Cooper

[Rich Feldman]

Since mild steel and low cost are under discussion, here are a couple of sources I've come across but not bought anything from.
Both offer mild steel and stainless steel spheres and hemispheres, 0.118" thick and up to 12" diameter, primarily intended for architectural and interior-decorating features.

http://www.kingmetals.com/default.aspx? ... 0Spheres*0@@

http://www.wagnercompanies.com/spheres_ ... heres.aspx

Any opinions on their suitability for DIY-fabricated high vacuum chambers would be welcome.
OK under the Subject of this thread, because the plain steel products are so cheap compared to the stainless. Maybe even neatly weldable at home with oxyacetylene.

Rich

[Jeroen Vriesman]

Electrolytic polishing might be more useful.
I am also using two big rotary valves to make a vacuum chamber, about the same size, and I think it's AK steel 400.
Do you have a picture?

[Richard Hull]

Regardless of price, SS is the best choice as all critcal mating, vacuum rated hardware is SS. If using steel, you will be doing a lot of machining and custom part work if your fusor is to be accessed for updates or changes, taken apart for servicing, etc.

Richard Hull