What's the best plate configuration for me?

[myoldyourgold]

Sounds like you left off the rinse step. You might need to start all over again. Rinse it off now and see what happens.

[nst6563]

I'd suggest a re-rinse also, if not a cleaning with a vinegar bath, then acetone, then re-passivate.

From personal experience...if you don't get all the citric acid off, you will get discoloration from the residue of the acid. Not to mention that with acid residue left on the plates the surface will not oxidize completely like it needs to.

When passivating the stainless steel the temperature of the citric acid bath should be kept between 140f to 160f for a period of 30-45 minutes. Longer could have negative effects, shorter could not give a complete passivation. If you're unable to heat the solution then let them soak at 70f-77f for a couple hours.

Here's a link to some documents I've collected with regards to passivation. None of them are very long, however one (from the aerospace industry) does go into some good detail as far as concentrations, temperatures, and the resulting thickness of the oxidation layers. It may help you with any questions you might have in the process.
http://www.mediafire.com/?bm1jwwwd5z5ht


Is there a way to post a picture of what you're talking about?

[myoldyourgold]

I'd suggest a re-rinse also, if not a cleaning with a vinegar bath, then acetone, then re-passivate.

From personal experience...if you don't get all the citric acid off, you will get discoloration from the residue of the acid. Not to mention that with acid residue left on the plates the surface will not oxidize completely like it needs to.

When passivating the stainless steel the temperature of the citric acid bath should be kept between 140f to 160f for a period of 30-45 minutes. Longer could have negative effects, shorter could not give a complete passivation. If you're unable to heat the solution then let them soak at 70f-77f for a couple hours.

Here's a link to some documents I've collected with regards to passivation. None of them are very long, however one (from the aerospace industry) does go into some good detail as far as concentrations, temperatures, and the resulting thickness of the oxidation layers. It may help you with any questions you might have in the process.
http://www.mediafire.com/?bm1jwwwd5z5ht

Excellent and accurate information. Thank you Sir.

[nst6563]

Excellent and accurate information. Thank you Sir.

Thanks - The devil is in the details

Speaking of passivating, I picked up my 36 plates today from being blasted and will be passivating them over the next couple days. I'll be posting some pictures when complete with the two methods I've been experimenting with. The blaster didn't do as good a job with the set of 36 as they did with the first example plate, but it's not very far off and I'm not going to complain for $50.

I'd love to get a multi-stage compressor + large Aux tank and do them myself. Heck I'd do other people's plates if I had the means.

[Sei Young Kim]

Thanks for the help! I can't post pictures tonight, but I will be able to soon.
I do have holes in my plates. I'll describe them best I can. I have three on the top and three on the bottom, parallel to each other. Reading around, it seems that putting Weldon 16 around the holes is a good idea. I'm not sure why this is though.
I have sanded my plates, but only a little and I guess sand blasting with nickel slag (or is it copper??) will do better for surface area.
I have no idea what passivating my plates means, so hopefully you can enlighten me
and the electrolyte I use is KOH with VERY small concentration. With the setup I've been using, it would draw way to many amps with even a 1/4 teaspoon per gallon of distilled water.
I've just ordered more parts, 14 more plates and the same gasket. Hopefully I can make this setup more efficient. I hope to save my other cell also and maybe use both at once.

I think your liquid concentration is too lean for generates more gas,
and plates should be in same gap even outsides also.

[cpaiin]

Ok, so I just finished passivating my plates and they are sitting in a tub of distilled water. Anything I should do next?

I do have another question. I bought a 750 watt computer power supply. I was planning on using that as the power supply, mainly because they are so much cheaper than anything else I could find. Since PSUs mainly give out 12 volts, what's the best number of plates and +/n/- configuration to have? I've heard something about 1.4 volts, but I don't know if that just means per per plate (so like only 8 or 9 plates in the system total) or if 1.4 volts is only divided up by the number of plates attached to a power source, whether + or -. I'm guessing this might be a difficult or just long topic to jump into, so if you could direct me to another thread or article, I would really appreciate it. Thanks!

[nst6563]

Make sure you rinse them thoroughly - do not touch with your hands - use gloves. Have access to pure o2 then hang them in a container and blow the pure o2 through it four a couple hours. If you don't have pure o2, hang them to dry - not near any other metals - for at least a day or two.


A computer power supply can be used. How many power 'rails' does it have? Depending on the psu design you may need some slight modifications. Some also allow you to adjust the voltage +-3 percent via pot on the circuit board.

The 1.4v you are referring to is the per-plate or plate-gap voltage. If you have 7 plates, 12v / 7plates = 1.7v.

[cpaiin]

I will dry them tonight.

The PSU, I believe, only has one rail. My plan was to strip all the wires and bundle the wires of the same color to a make terminals. Since I bought a 750 watt psu, which would give up to 60 amps, I feel that 8 plates might not be enough (though it's only a feeling, not based on anything I really KNOW. I'm afraid the unit might become too hot). Since I recently bought 14 more SS plates, would it sound like a good idea to use 3 separate, smaller PSUs? This way I would have about 20-30 amps running to each 8 plate setup. I would set it up so that all three cells would combine gasses to a single line.

I'm 100% open for suggestions. And thanks for all the help so far!

[nst6563]

There are pros and cons of the pc psu. Check the load ratings label on the side. +12v is really what you're going to be concerned about. Some psu's have seperate rails to power the motherboard and video card seperately from the rest of the system. There is a way to utilize both 12 and 5 volt lines but it would require the use of more circuitry to increase the voltage and diodes + fuses for protection.

Do load testing on the psu as well. Many show very stable voltages under average conditions but when a very heavy load comes into play the voltages start fluctuating - sometimes to extremes and even failure.
The load testing may also reveal that the psu has degraded rating in your environment. Unless you can determine if the psu ratings were tested in accordance with a "normal" room temperature condition I would drop 75w from it's rating. The colder the test environment, the higher it can be rated etc...

I'd stick with the one cell you have for now. Get it running as best you can - overcome any hurdles with it. Once you're happy, build another like it to duplicate the results and run them in parallel.

[jannypan]

The +-+- type of config is known as brute force and normally requires a PWM to control the heat (usually generates really good productions though)