Brooks,
Larger cells will allow you to run larger batches, but strip times are relatively consistent.
Think of it like this:
It takes a well defined finite amount of electrical current to plate an atom of gold on the scrap, and it requires the same amount to remove an atom of gold in the cell. Therefore it takes the same amount of time at the same amperage to strip the gold regardless of cell size.
You can't increase the rate that the gold strips by increasing the cell size unless you also increase the current density ( and the heating) between the anode and cathode. It's very important to size all aspects of the cell accordingly: power supply, volume of electrolyte, and amperage. If you do not increase the power supply current enough to compensate for the larger cell, hence larger between anode and cathode, you will actually slow the rate of gold stripping. If you do not increase the amount of electrolyte proportional to the cell size the electrolyte will heat quickly and you'll be replacing larger parts that wear out due to corrosion.
You'll need enough cell volume and design to allow for exposure of the electrolyte to all the plated items so they all strip. otherwise you'll end up with a high percentage of stripped scrap that does not strip. This is evident in the small cell, if you have tightly packed scrap like small fully plated pins, the electrolyte does not make electrical contact with all of the pins and therefore does not strip them. These pins are in effect protected from the current of the cell. On the same track, the basket, if not properly formed around the pins will shield the pins in a 'Faraday Cage' that prevents the electrical current from passing through the pins to promote timely stripping of the scrap. The current will flow through the basket instead and decay it. This is known as the path of least resistance.
My advice is to learn the factors that affect the efficiency of your small cell, then redesign a larger one that overcomes the bottlenecks that are destroying your anode, causing heating, and slowing the overall process. Your corroding basket indicates an operational flaw to me, not a problem with the basket material.
A well balanced cell is a trade off between amperage flow, electrolyte volume, anode and cathode surface areas and configurations, scrap exposure to the electrolyte and electrical current, and proper temperature control regardless of it's size. Scale up in steps to be sure your new designs are sound in all of these aspects.
For me personally, it is better to 95% strip a 1/4 to 1/2 pound of plated scrap in small cell in a few minutes then cool the cell and reload, than to spend the effort to build a larger cell that takes days to 95% strip a few pounds of plated scrap. Keep in mind the larger cell means larger volumes of sulfuric acid to filter, transport, and recycle. Again the larger cell takes the same amount of time to strip the same scrap at a given current density (amps per square inch) regardless of the size of the cell.
The larger cells offer advantages in the time required to monitor the cell operation. They can be loaded, set to run, and left on a timer to complete after a trial run to determine the safety of the set up. You will still have some percentage of the scrap that remains partially or fully plated. Scaling up is perfectly feasible, but not as simple as you may imagine.
One last thing to think about is the time between clean out the cell and batch processing. Large cells do not lend themselves well to determining actual yields for a particular type of scrap. The small cells are well suited to this since they are easily cleaned out. A large cell takes longer to become saturated with gold, so your values will be tied up in the batch.
All in all it's a trade off between your goals and the proper size of the cell you design.
I hope this helps. I'm hoping others with cell experience will post their suggestions also as this is only my take and guys like GSP and Oz will surely provide some different angles on the benefits and problems than I do.
Steve
