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topic 2593

Porous Pots


Presently we are using 3 porous pots to oxidize tri-chrome to hex chrome with very little success. We run the pots at 6 volts/200 amps. with 15% sulphuric acid solution in the pots. These pots are used in a chromic/sulphuric etch bath for ABS/PC plastics.Tank volume is 3,000 gals.

Any suggestions.

Keith Guppy


You do not say whose pots they are or what size they are or the total amount of trivalent you are trying to convert in what time period. Also , how new are they. The pores can plug up and efficiency drops way off. I suspect that your reaction with the plastic is generating a lot more trivalent than you think. An obvious solution is to go to more pots if three is not enough. On chrome plating tanks, we just used the plating solution in the pot and dumped it when it was slimy. You may have to dump the inside more often than you are doing now.

What does the vendor of the pot have to say?

James Watts
- Navarre, Florida

August 5, 2009

Not knowing how high your tri-chrome has reached my suggestion would be to increase your sulfuric to 30%. 15% maintains your opt range once it's reached however 30% will help you to begin to lower your tri chrome.

Tim Roy
Plating on Plastic - Nicholasville, Kentucky


We hard chrome plate and grind and are currently using a porous pot in one of our chrome plating baths. I would like to know how to make a porous pot from scratch as opposed to purchasing one for each tank.

Howard Larsen
PLATING & GRINDING - Muncie, Indiana,


I seriously doubt if you can make one cheaper than you can buy a rudimentary model (from suppliers who make this product).

James Watts
- Navarre, Florida


If you really want a cheap system go to your garden centre and get a flower pot - not the plastic type but a proper old ceramic type. Thoroughly wash it with acid and alkali cleaners and leave it in soak for a few days, regularly changing the water. Stick a rubber bung in the drain hole and hey presto - a cheap porous pot. I have used one for a divided cell in a small plating bath using trivalent chromium without any major problems. I don't know how long the pot will withstand the process, but in the short term it worked. Don't tell the membrane manufacturers though, they may corner the market for flower pots and upset us gardeners!

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

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