Using a Mag Drive pump for electrolyte circulation

[NeoMoses]

Currently I do not have any type of agitation in my anodizing tank. I have a couple of mag drive aquarium pumps and was thinking about using one for tank circulation. Is this a good idea? They have plastic bodies, plastic impellers, and ceramic impeller shafts.

I'm worried mainly about corrosion of the magnet. Will this happen?

[NeoMoses]

I'm guessing that from the lack of replies, nobody else has tried this. Also, since aquarium pumps are not usually used in corrosive environments, I'm seriously doubting this is a good idea, so I'm planning on steering clear of it for the time being. Perhaps I'll get a bubbler like Fibergeek used in his setup, or possibly an all-plastic pump rated for use with acids.

[Fibergeek]

NeoMoses, wait a little longer.

Someone (not me) is working on this. He will be ready to publish his results shortly. I don't want to upstage him. It's cheap, very clever, and better than the aeration system I used.

[NeoMoses]

Sounds good, Fiber. My other idea was to build a small plastic paddle and place it in the tank... But, if there's an inexpensive and relatively easier way to do this, I'm all ears.

[neilfj]

I've been working on this issue, and rather than using aeration, agitation would probably be a better solution. Sorry I wasn't able to respond earlier, but I've been having other issues with my setup (not related to the agitation/aeration). This method appears to work very well, but be cautioned that it is still being tested and there may be modifications to it based on actual results.

What I used is a Boyu 1300B Pump – 900 lph (15 Lpm) Outlet Size: ½” ID 5/8” OD

The aquarium pump won't move enough air to get good aeration and I believe Caswell is going to use this pump as a replacement for the air pump currently supplied with the LCD Kit. I don't want to speak for Caswell, so don't take this as gospel. The pump includes a filter canister and an additional pump base that allows it to act as a water powered suction pump and add air to the water stream. Don't use this part.

The pump works by induction and only has a single metal part exposed to the electrolyte, which is the drive shaft. The shaft seems to be impervious to the electrolyte as I've had it in the solution for over a month without any negative effects (in normal circumstances, I'd recommend removing the pump from the electrolyte when not being used).

In addition to the above pump, I got a 25’ Roll ½” OD /3/8” ID Polyethylene Vinyl Tubing from Home Depot #42141525 - $3.58 (This is not clear tubing, but the stiffer, milky white tubing).

Cut a 4ft section of polyethylene tubing. This is sufficient for the 5 gal buckets provided in Caswell's LCD kits. You may be able to get smaller amounts from ACE/True Value stores rather than buying the 25’ piece.

Remove the filter canister from the pump and make sure that the aeration housing is not being used.

Use piece of plastic bag or saran wrap to wrap around end of polyethylene tubing and friction fit into output of pump. Be careful not to split/crack output nozzle of pump. Use a threaded plastic cap or similar to seal the far end of hose.

Remove strainer basket from pump and lay the pump on its side in the bottom of the bucket, with the suction nozzle pointed to the middle of the bucket. Coil the tubing inside the bucket so that it wraps like a spiral up the side of the bucket. Friction and the natural curl of the tubing should keep it in place until adjustable cable holders are installed. Take a marker and run it against the inside edge of the tubing. Remove tubing and using a 7/62” drill bid, drill about 14 holes along the inside line you drew. Space the holes evenly the length of the tube, leaving 6” un-drilled on the end that connects to the pump.

This will cause streams of water to be directed to the center of the bucket ensuring sufficient agitation. Install a ½” plastic cap on the end of tube, or something similar to seal the end. A plastic foam earplug fits nicely.

Too many holes or holes that are too large = reduced pressure and not all holes will produce water streams. Too few holes or holes that are too small will cause higher pressure streams of water which could cause splashing and spraying. Make sure you drill the holes on the inside of the coils, as mislocating the holes to the top of the tube would cause electrolyte to spray up and out of the bucket.

Fill bucket with about 5" of WATER and test. You'll be able to see the direction and strength of all the streams and you can decide whether you need to add more holes to the tubing or plug some of the holes you already made. Once you are satisfied with the condition of the tubing, fill the bucket completely. You should be able to see shadows in bottom of bucket showing the agitation.

One benefit of this method is that you have a number of options and flexibility. You can adjust tubing to the amount of fluid in bucket by spreading out the spiral to take care of a full bucket, or compress the spiral for ½ full bucket. If needed, you can use a longer (or shorter) piece of tubing, depending on your situation.

Make supports for tubing. Cut (2) 2” strip of lead and fold down the middle. Drill ½” hole 1” from the bottom end, then every 2 inches. The hole should be located and slightly touching the folded edge of lead. Use razor knife to cut & trim the holes and any flash left from the drilling operation.

Open fold so if forms a ^ then bend the edges so it looks __/\__ Run tubing using every other hole so that the tubing spirals up the bucket. The tubing will now be supported and can be adjusted by using different holes. Assemble and add 1 gal water to test to make sure everything works.

You can also use 8 ga aluminum wire from Radio Shack to make hangers to hold and support the tubing.

[Fibergeek]

I concur.

Given the choice, agitation is preferred over aeration. Agitation; if done properly, produces no or almost no acid mist. If a chiller is placed in series with the pump output, it's also a natural for forced electrolyte cooling. This is desirable if you intend to go to high current densities, your work is large, or you want to grow a really thick Type II coating.

I intend to convert my setup to Neilfj's agitation method, the intermittent racket from the (aeration) air compressor cycling will drive you nuts.

I just noticed a spelling checker; how nice, thanks Lance!

[whistule]

Neil, I presume with the new you would need a pump for each tank? I am not doubting your method but from here it looks like it's more expensive for not much gain. ??


Fiber, I have found that an aquarium pump runs pretty silently in the background - presumably there is some reason you have used a compressor instead. I was thinking that a compressor might be the way forward rather than buying loads of air/water pumps for each tank but your comment about been driven mad has made me think twice and I was never too sure how to reduce the airflow from a compressor with an air tank at 150psi or thereabouts.

[Fibergeek]

Yes, aquarium air pumps run silently.

Unfortunately, I haven't found one even remotely powerful enough to properly aerate a 3 gallon (11 liter) setup. I tried a Rena Air 400, which was the largest (150 gal. aquarium) and most expensive ($50.00 US) model carried by Petsmart, which is a large petshop chain. I don't know what this pump's air pressure (PSI) or capacity (CFM) is. What I do know by experiment, is that it needs to be at least 10 times more powerful for a 3 gallon setup.

With either aeration or agitation; if you can see any hydrogen bubbles sticking to the work during anodization, your method is inadequate.

What I settled on for aeration in my 3 gal. setup, was four 1/2" x 14" plastic "bubble walls" driven at 20 PSI (5 PSI each) with a capacity of 7 CFM. The compressor cycles every 10 minutes or so. 5 PSI is the maximum these bubble walls will take.
At this level of aeration, mist generation is severe enough to wet surrounding surfaces within a few inches, causing a sneak path between the anode and the cathode, shorting out the power supply. Using mist suppressant and mist balls will keep the misting down to a manageable level. The PITA the mist causes, and the racket of the compressor cycling, is why I don't like aeration.

BTW, my air compressor is rated for 7 CFM at 90 PSI, is 3 HP and has a 12 gal. air tank. It has a knob to set the outlet pressure down to 20 PSI.

Neilfj said that his aquarium water pump is rated for 900 liters per hour (240 gal. / hr.) This will recirculate my 3 gals. of electrolyte in 45 seconds. If you use something like Neilfj's spiral, the electrolyte is moving around real fast and evenly, but the surface of the electrolyte barely has even small ripples on it. No mist generation at all. Do you really need a pump with that much capacity? I don't know. As long as all of the electrolyte stays in the tank, you can't have too much agitation. Petsmart lists a pump of similar capacity for about 30 bucks.

As Neilfj also said; do all of your agitation testing with plain water, a mis directed hole can squirt a stream 10 feet out of the tank!

[neilfj]

Like everything else, it depends.

I found the agitation method to be cheaper and more flexible. The pumps are inexpensive (approx. same cost as aquarium pumps), and the tubing at $3.50/25' is cheap too. The reason I didn't use the aeration method was because the aquarium pumps did not provide enough volume of air to properly move the water around, nor did I have a compressor. I also found that the airstones used by Fibergeek (approx. $3/ea), and the quantity needed to provide adequate coverage makes aeration much more expensive. In my case, the agitation method also took up less space in the bucket than did the aeration method. Weighing down the airstones to eliminate the bouyancy was also a pain to deal with.

It's a matter of economics and scale, each situation will be different. For the small scale home/hobby anodizer the agitation method is easier to setup, cheaper and has the added bonus of reducing misting and you can watch the process if you are so inclined. Not that there is much to watch, but with the aeration method, you can't see your work piece due to the bubbles.

Multiple tanks or large tanks can be accommodated by either using higher capacity pumps or multiple small pumps and it may be more cost effective to use aeration for these type applications. But, in these cases, rather than using any pump and tubing at all, I would probably use a mechanical agitator. Since the purpose of both aeration and agitation is just moving the water around, even a paddle wheel attached to the end of a small motor or a variable speed electric drill would provide the movement required.

Multiple tanks would require multiple pumps unless you have a central reservoir of electrolyte, along with a method to drain off excess solution from your anodizing tanks to feed the pump. This isn't something I was attempting to address with this method, but was more geared to the hobbyist/small scale anodizer.

For me, using the LCD Kit sold by Caswell with the 5-6 gallon bucket for anodizing, the agitation method is just plain cheaper, easier to set up and safer to operate.

[whistule]

Yeh, I see that agitation is certainly preferable if possible. In my case my tanks are 50 litres and rectangular (shaped a bit like a kitchen bin). I have cut a thin strip of aluminium (obviously titanium would be preferable) and bent it to form a rectangle and then drilled and woven the air line through the aluminium. The airline runs down the side of the tank - held in place by an aluminium wire - and the rectangle sits idle just off the bottom of the tank and when you fire it up the force of the air pushes it right against the bottom.

I only have one electrolyte bath but I also aerate my degrease, sealer, dye and rinsing tanks - I thought you would be the same ? I can do the whole whole lot from one 4 port air pump so I guess this would be cheaper for me.

Having said all this my only proof of the fact the system is moving the electrolyte about enough is the quality of the anodising. As you say it depends on the system so I am only really posting this for interests sake and for the benefit of those who might have a similar type of system to myself.