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Electroplating inside of a tank

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Turkey9

Sun Oct 25 2009, 09:47PM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

Hi!
I'm looking at the possibility of electroplating the inside of a steel tank for use in a vacuum system. I was thinking:
Stainless steel is usually used in vacuum systems because water won't impregnate easily into it... Aluminum and copper have similar properties.... Because I need such a large chamber size, I want to use a prefabricated compressor tank that is made of mild carbon steel. If I electroplate the inside of the tank with copper or aluminum I won't have the issue of the steel tank walls absorbing water vapor.

My question; how would I go about electroplating the inside of a 14 gallon tank? I would like to use the safest chemicals and don't need a perfectly polished finish, just a solid layer of copper or aluminum. Electroplating material isn't too important as long as it is suitable for a high vacuum.

Thanks!
-Jesse

rp181

Sun Oct 25 2009, 11:11PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

Home electroplating usually does not turn out well, or even, probably not good enough for vacuum. Commercial electroplating uses cyanide based solutions.

just my $0.02

3l3ctrici7y

Sun Oct 25 2009, 11:37PM

Registered Member #1806 Joined: Sun Nov 09 2008, 04:58AM
Location: USA
Posts: 136

Copper electroplating is pretty easy.
I'm not sure about alum.

There are some good youtube videos showing how to do it.
Stand by and I will find the links.

eta; here we go;

Both authors have other copper plating relevant videos.

Have fun :)

MinorityCarrier

Mon Oct 26 2009, 01:01AM

Registered Member #2123 Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312

Commercial electroplating is not limited to cyanide solutions. I am responsible for gold electroplating at my job, the chemistry used is Sodium Aurisulfite-based, pH of 9.5 (fairly safe to work around, no annoying facility evacuations due to cyanide gas release if someone makes a mistake).

There are also electroless copper plating chemistries. Spend some time doing the research. You may need to plate an adhesion layer first.

I'm not familiar with aluminum plating, but it apparently is done.

The requirement for good electroplating is CONSTANT CURRENT, not voltage. You will need a constant current supply.

klugesmith

Mon Oct 26 2009, 01:45AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

I believe it's impossible to electroplate aluminum from an aqueous solution. Al is on the wrong side of hydrogen in the activity order -- sorry, don't remember the proper words. Electrolyte chemistry for plating Al is related to that found in lithium batteries.

I wonder if your carbon steel tank, after a nice pickling of the interior surface, could be pumped down enough to -evaporate- a coating of liner metal?

Turkey9

Mon Oct 26 2009, 04:57AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

Thanks for the replies! From the research I've done, it seems that there are a lot of different electrolytes that can be used. What one do you guys think would be the best? It would be nice if it can be made cheap.

The only requirements as far as even coating goes, is that it is at least thick enough to polish slightly and that it also sticks. An adhesion layer is not out of the question if that is what is needed.

Proud Mary

Mon Oct 26 2009, 05:23AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Honestly, Mr Turkey, it seems unlikely to me that your plated lining would survive baking out, gettering, and all the other high vacuum procedures, even if it looks OK to the naked eye.

Though there are patended non-cyanide copper-plating-on steel- processes, it wouldn't be realsitic to imagine that anyone would be wholly successful on a first attempt: cheaper by far, I would guess, to make a vessel of sweated copper, and forget the electroplating altogether.

klugesmith

Mon Oct 26 2009, 06:00PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Hi Jesse.
How do you know that plain steel will be a problem, aside from getting rusty?

How about using a water heater tank as a vacuum vessel? If not made from stainless steel, I think they're internally plated or porcelain-lined. As in
Stong, C. L. and Settles, G. S., "How to Build a Wind Tunnel that Achieves Supersonic Speeds with a Vacuum System," Scientific American, Amateur Scientist Section, Vol. 215, No. 10, October 1966.
Stong wrote the regular Amateur Scientist column, and Settles was a high school science fair winner -- now a senior professor at Penn State Gas Dynamics Lab.

Turkey9

Tue Oct 27 2009, 06:24AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

Hmm... doesn't look promising. I was actually first considering lining the inside with a ceramic or possibly a bake on teflon spray... does anyone have experience with these sprays? I think i'll polish and sweat the inside of the tank and see how that works. If i can't live with the results, I'll find a way to coat the inside or look into getting a length of stainless steel pipe. After all, I don't need a perfectly non-contaminated environment and if all the steel does is cause a longer pump down time, that'll be allright for now. Thanks!
Jesse

Proud Mary

Tue Oct 27 2009, 06:30AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

May I suggest you first define what you mean by 'vacuum' - in millitorr - any good advice will depend on this

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