View Full Version : Question for Evan or...

03-28-2004, 12:50 AM
Do you EVER sleep...LOL.. Real Question..I asked about an anodizing setup awhile back. You say you keep yours outside. Do you just leave the acid etc. outside in the winter also? Or pour it into some kind of container to store it? I assume it won't freeze but was wondering if condensation would be a problem? Oh yes...and how do you get good contact on a part that has no holes in it to wedge the wire in or a solid part that is visible on all sides? Thanks

03-28-2004, 01:20 AM
Hi Russ,

I've been machining all evening. I set up my anodizing gear outside on a 4x8 sheet of plywood on sawhorses. The solutions are kept in well labled 2 gallon icecream buckets with snap on lids. I use a lye bath to preclean and microetch the parts lightly. At the end of the year I pour the lye bath and the acid bath together in a garbage can. They mostly neutralize each other. It sure looks cool, it foams up with aluminum colored bubbles. I then add enough sodium bicarbonate until the acid is completely neutralized. The resulting solution is pretty harmless consisting of aluminum sulphate, evolved cabon dioxide, sodium carbonate etc. It's safe to dump on the ground.

The problem with making good contact is a tough one sometimes. No matter how you do it wherever the contact is made it won't anodize at that point. Also, the contact not only must be good but it must be able to carry the current which may be considerable. Usually a part will have some sort of hole, usually a threaded hole which allows for dead soft aluminum wire to be screwed into the hole. If a part is to be anodized it pays to design in advance for the contact point.

03-28-2004, 02:35 AM
Thanks Evan! Say, do you use pure lead or aluminum for the cathode? I've been trying to find some pure lead. I have lots, used to use it for making shotshell shot but it's all melted down wheel weights and isn't pure. I'm getting quite a pile of things made that have to be anodized and it looks like some things are going to be a real problem to get good contact. Probably will end up drilling holes in some. I like your idea about using ice cream buckets. Are they 4L size? I was going to use 5 gallon containers but most parts are small so 4L would work fine. I hadn't even thought about getting rid of the acid...good tip! Thanks again!

03-28-2004, 04:39 AM

The buckets are about 8 litres I think. Just the right size for most projects. I don't bother with lead, I use aluminum flashing for meant for roofing. Use at least an amount equal to the total surface area of the part, more doesn't hurt. I just take a piece and curve it to fit the inside circumference of the bucket. It will get sort of cruddy after a while so take it out of the bath and scrub it with a plastic scrub brush, rinse and return. Remember, the acid concentration is pretty weak but it can make impressive holes in your clothes. Also, it evolves acid mist so stand upwind.

I use some 1/8" aluminum welding rod across the top of the bucket to hang the parts from. That is where I have had the most problems with connections. I use a knife to scrape the wire clean to bare metal and hook the drop wire over the cross wire, bend it down and hold in place with a wooden clothspin. Find an electrical contractor and ask him for a short length of aluminum electrical cable, they still use it for drop wire. It is pure aluminum and works the best for connections. You should be able to get it for free.

You can easily tell if the connection is good, it will fizz like crazy for the first 20 minutes or so. If it stops fizzing sooner then you probably have a connection problem. I use dishwashing gloves to handle the parts. It is important not to get any trace of body oil on anything. If you have a total anodize failure you can dip the part in the lye bath, strip it and start over again. You will loose a few thou but that's about all.

I pretreat my parts in the lye bath, about 1/4 cup of lye to two gallons of rain water. Drop the parts in until they are fizzing well, then rinse well. This will not take the shine right off a part but does ensure it is clean.

03-28-2004, 12:37 PM
Evan,have you noticed any difference with temperature?Is colder water better?

03-28-2004, 12:40 PM

Yes heat affects the process.. Too fast anodizing changes the temperature/ph to where it eats off as fast as it adds on.


03-28-2004, 12:56 PM
Evan, Thanks again!
Weird...good question...I was wondering if the results would differ if you used the process at different temps...you would almost surely run into that with the setup outside.

03-28-2004, 01:58 PM
Yep, temp most certainly does affect the process. In the summer when it is warm I put the acid bucket in a tub with ice and water. The process liberates a good deal of heat. The acid bath must be kept at or below around 25C (72F) or it gets ugly. For hard anodizing the temp is held much lower, less current and much longer time.


[This message has been edited by Evan (edited 03-28-2004).]

03-29-2004, 12:35 AM
Thats what I was thinking cold would be better.I have a friend with some r-12 water coolers that he convertd to freeze-12 or some other substitute,they have a stainless pot wrapped in a copper coil.The coil can be unwound and added onto,I'm thinking a aluminum stock pot for the outside container and then set it up double boiler style with a five gallon bucket for the business end.Two of these mounted up in a insulated plywood box would probibly be way cool.As they stand now you can dump a gallon of water into them and they make an ice ring around the top in about three minutes,they also consume very little in the way of electricity,about 1-1/2amps@110vac.