We seem to be hijacking Kevin's thread and arguing back and forth...So, to bring your question to the surface and answer it again Kevin :
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Originally Posted by anodizeme4ever
Can anyone tell me which makes the best cathode - aluminum or lead? I'm in the process of setting up a large rectangular tank and want to make sure I have the best before proceeeding(for obvious reasons).
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My suggestion to you is to call your local anodizing outfit, heck call several. Ask them what they use for cathode material. If it is a modern shop (chances are even if it is an older shop), the answer will almost always be that they are using a 6000 series aluminum for their bus bars
and cathodes.
They must be using aluminum for a reason...Fact is, its for the same reasons I mentioned above.
- Efficiency (less electrical resistance)
- Heat build up (due to the electrical resistance being lower)
- Less recitifer strain (due to the electrical resistance being lower)
- Avoids lead contamination
- Ease & economics of waste water treatment (lead free)
It is true that I have never used lead as a cathode in my operation. Having said that, I can't think of one single benefit to using lead over aluminum. Someone said that lead lasts longer. This may be a possibility (and it may not be, for argumental purposes I'll go along with it) but when you consider that your cathode MAY need to be changed once every few years, I'm not sure the pros out-weight the cons here.
And in direct response to some of your comments cameraman :
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Originally Posted by cameraman
I said that you aren't going to try to get rid of it until you've anodized several hundred square feet. The point is that it doesn't pose a problem until you need it to go somewhere else. Unless you're staring at an LCD screen, the CRT monitor you're looking at right now contains lead, barium, cadmium, phosphorous, and mercury. While it's sitting on your desk it isn't a problem. If you throw it in a landfill when it dies, it becomes a problem. Likewise, the lead sitting in the bottom of the tank isn't a problem while the solution is in service - and actually, we don't even know at what rate that's happening - it's quite possible that we're only looking at 1 ppm after 1000 square feet. I don't have a rinse tank. If my ano tank ruptured, I'd clean it up.
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It may be true that the CRT monitor that I am looking at right now contains lead in conjunction with several other deadly chemicals, however, the same monitor I am looking at was engineered to safely contain these chemicals. Furthermore, this same monitor was tested prior to marketing to ensure a safe product. Engineered and tested! Going on, each and every monitor which has hit the store shelf has passed a Quality Control process in which the entire product is inspected for defects. Needless to say, a monitor posses much less risk of accidental leakage than say something such as a home made anodizing tank. The chance of accidental leakage, rupture, spillage, dragout are much greater with a large, open container - particularily one which has not been engineered or tested for the specific task at hand. Bare in mind that you are not in direct contact with the chemicals inside your monitor. You are in constant proximity to the chemicals within your anodizing tank. My last point will be this...Regarding your CRT monitor, when it does cease to function and it is no long of any use to you - generally it would go to the dump. Every landfill I've been to in the last few years has a designated place for things of this nature though some people choose to kick them off the back of the truck and bury it under more debris. Thats what those filthy people who work at the landfill do...They are paid to be responsible for those of us who aren't. They pick your monitor out of the trash pile and seperate it. Bottom line, it falls on the responsibility of the individual...
I recognize your point here cameraman. You argue that the solution shouldn't become a problem until your choose to dispose of it. I don't disagree with you, however, I also feel that one should take into consideration the "act of god". Accidents happen and I strongly feel that one should be prepared and educated for such an event. You suggest that in the event that your tank raptured that you would simply clean up the spill. Do you know how to clean trace amounts of lead from off a concrete floor? You also bring to the table the possibility of there being only 1 ppm lead in the solution after anodizing 1000 sqft of material. Regardless of the quantity, it is still a regulated waste.
You say you don't have a rinse tank...I must assume at this point that you rinse your parts after anodizing under the tap. Where do you think those contaminants go when they run down the drain? They don't get delivered to the hazardous waste tratement facility thats for sure...Agreed, the quantity of lead may or may not be very minute, however, it all adds up at the end of the day...
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Originally Posted by cameraman
Well, I guess we'll just have to agree to disagree there. The only way my stuff would end up in the sewer is if the hazardous waste people put it there.
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I won't disagree with you but rather bluntly point out to you that you are wrong. It would seem as though that you have a difficult time accepting that. We all do from time to time and I'm no exception. The only reason I can say to you that you are wrong with any confidence at all is that I had a meeting not too long ago with a few representatives from my city council. The individual responsible for environmental sewer control directly told me that I could dump up to 40,000 gals of my anodizing baths directly into the sewer system providing that their pH levels were adjusted accordingly. That's not to say that I do dump my baths into the sewer but rather I could if I so choose. I later went on to speak with a local hazardous waste treatement facility here in the city and was told the very same thing. So infact, if I did bring my solutions to the hazardous waste facility, I would be paying them to dump it down the sewer (after pH adjustments of course). Simply put, where I am located, your statements do not hold true sir.
I will take this time to apologize if I seem to be coming off like a "pushy, know-it-all". My intentions are good I ensure you cameraman and infact I make no claim to "know-it-all". Quite the contrary as a matter of fact. As I have made anodizing my full time job and my life, I learn new stuff regarding anodizing on a daily basis. I did in fact point out to you that you were incorrect in regards to sewer dumpage, however, I also realize that the regulations may be very different in your current location. I accept and apperciate your arguements. The way I see it we can learn much from eachother.
Good luck anodizeme4ever! Let us know which road you travel...
- Dan