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Anodizing Using alternatives other than sulfuric acid

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xalky

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Everything has it's dangers. Good common sense, and safety consciousness, goes a long way towards avoiding dangerous situations.

When dealing with hazardous chemicals here are some things we should be doing:

*wear safety goggles
* wear some good quality rubber gloves, and make sure they are up to the task of handling the chemicals your using. Some acids are not compatible with certain glove materials, and will eat right through them.
*Good ventilation is a must, or better yet, do it outside. If you must do it inside make sure that your ventilation is up to the task of evacuating and drafting in the immediate area of your chemicals when they are open. For some chemicals that cause particularly noxious fumes, a resperator in addition to the above should be used.
* make sure that you have some running water nearby, just in case there's a mishap, that you'll be able to rinse immediately.


These are chemistry 101 safety measures.

Marcel
 

refinery Mike

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I have a question on the sodium bisulfate anodizing. Do you use some method for keeping the solutions at the anode separated from the solutions at the cathode. Such as a semipermiable devider. It would seam to me that the current that produced the SO3 ions would also create NaOH on the other side and contaminate the solution.
 

eac67gt

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Hi Mike. Being I am only an experimenting hobbyist I myself can't totally answer your chemistry question. What I do know is what I am doing "seems" to be working fine. I have run a lot of parts through the same bath and it is still working great. The only thing between the anode and cathode is the solution itself. I don't recall in all my searching on the internet any semipermeable divider in any anodizing solution being it sulfuric acid or sodium bisulfate. Sorry I couldn't really answer your question. I am always trying to search topics on anodizing so if I come across something on this question I will try and answer it.

Have a great day!

Ed
 

PurpLev

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Ed, what brand/product did you get for anodizing?

I went to HD today and they said that all pool supplies are not currently stocked (a seasonal thing) but suggested I'll look online and see when it'll be available. I did search online, but did not find anything that is related to 'sodium bisulfate' on HD website, and neither on Lowe's so was wondering what the name of the product you were able to find and use?

while searching online I did come across an interesting fact about sodium bisulfate - it is actually a by product made from a chemical alteration of none other than sulfuric acid (resulting in sodium bisulfate and water). Not that it matters much as after the chemical change it is no longer sulfuric acid, but I did find that an interesting fact.
 

eac67gt

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Try this. It is actually what I bought at Lowes. They told me the same thing as far as pool supplies but this is the right stuff.

As far as sulfuric acid or any other acid an electrolyte can be many different things. The process as far as time, current, voltage, solution mixture ratio are just different. I was doing a lot of investigating today also and as long as you can get that crystallian layer to build that is really all that matters. There was also some concern over fading of color. If you are going to have the anodized item outside constantly subjected to UV or salt then fading can occur but otherwise it is not an issue. Like on a friends gun that I did a laser mount for, it will spend most of its time inside compared to lets say a part on your car so being dyed as I did it is not an issue.

Give this a try for the sodium bisulfate. The other place to come by it is Ebay.

http://www.lowes.com/pd_220862-1772-07466000_4294936849__?storeNumber=2372&Ntt=ph+decreaser&selectedLocalStoreBeanArray=%5Bcom.lowes.commerce.storelocator.beans.LocatorStoreBean%4064d464d4%5D&pl=1&productId=3025118&ipTrail=174.55.58.63&currentURL=%3FNtt%3Dph%2Bdecreaser


Ed
 

PurpLev

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Thanks. I've found some on Amazon somewhat a bit more cost effective (if you should need more):
http://www.amazon.com/Kem-Tek-042-6-Minus-Chemicals-Pounds/dp/B000HJ7CE6/ref=sr_1_1?ie=UTF8&qid=1363546920&sr=8-1&keywords=sodium+bisulfate

All these discussions about electrolysis solutions and what not made me question if you might be able to use white vinegar (acidic) with good results. Although I would think this is nowhere close to the concentration power of the sodium bisulfate or sulfuric acids. anyone tried this before?
 

eac67gt

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Glad to see you found what you need.

No'op haven't tried vinegar but I am curious. Maybe I'll have to give it a try for fun.

Ed
 

PurpLev

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I tried last night with a bath of sudium-carbonate (washing soda) with poor results. the problem right now is that I don't have things setup properly so there were too many variable that could have been the culprit.

the reason I used this is because this is what I use for cleaning rust off of ferrous metals, and the idea is very similar. I did some research and sodium is a common soluble for electrolyte solutions.

I was using a 400WA PC power supply (12v) which I use for electrolysis but could not get any Amp readings. either my amp meter is faulty, and/or I just wasn't pushing enough Amps to make a difference, but I did not see a bubbling action that I normally see when I had a test Alum rod as the Anode put into the solution (I did get bubbling when I put a different piece of alum in there... I'll have to retry). left if for a couple hours and got very mild results - the surface is slightly tinted but blotched (ok... I didn't properly clean the part either as my test was just to see if I can get enough current through this solution more than anything).

I may need to get a "proper" power supply and start eliminating all the variables in my equations. once I get a 'good' anodized part, I'll start changing solution / power supply so that at least I'll have something to compare it with.
 

eac67gt

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Purplev brought up seeing that vinegar could be used for anodizing. He saw it somewhere on the web as I have also.
Being an experimenter and hobbyist I though I would give it a try.
Remember I am not a chemist or engineer this was just for fun.
I used two pieces of aluminum just like I would for sodium bisulfate or sulfuric acid anodizing. One for cathode and one for anode.
This time I used 20 vdc supply at about 200 ma. (small pieces)
I used distilled vinegar straight up in container.
Here are the pics and a video at the end showing the hydrogen bubbles while power was hooked up. It looked like it was doing something????
In my opinion, but I don't know if I did it right, it failed miserably. Ran it for 4 hours with no signs of crystalline layer building up.
Dye did not take even close to correct. It should have been a dark blue.

Ed

Setup
IMG_2184.JPG
properly prepped piece
IMG_2166.JPG
after anodizing
IMG_2202.JPG
after dyeing
IMG_2206.JPG
the video
View attachment vinegar.mp4

IMG_2166.JPG IMG_2184.JPG IMG_2202.JPG IMG_2206.JPG
 
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eac67gt

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I posted up a question on Finishing.com. Here is the copy and paste of the posting. Though he did not say a lot he did not condemn using sodium bisulfate in anodizing nor did he have issues with sealing in boiling water. In my opinion the methods I am using are fine for aluminum anodizing in the hobbyist world.

I will keep an eye on this post because others will read and add to it, hopefully. :))

Ed

Q. I am using sodium bisulfate in anodizing tank. Pros - cons?
Also I seal parts by just boiling. Pros - cons?
I am making parts of aluminum 6061. They are not being exposed to harsh environment.
Any input would be appreciated.
Have a great day!
Ed

A. Hi Ed. Personally, I've never heard of using sodium bisulphate for industrial aluminum anodizing, but I do hear about it in the hobby world. It's an intriguing idea, and I'd love to hear of some comparative tests for salt spray resistance, dielectric resistance, color retention, etc., (none of which may be especially important to you though).
There is nothing wrong with boiling water sealing at all. It's used industrially for clear anodizing, but it's best if you have de-ionized water. Good luck.
Regards,
mooneybeach2sm.jpgtedsig.png
Ted Mooney, P.E. RET
finishing.com
Brick, New Jersey
 

eac67gt

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I tried last night ....but I did not see a bubbling action that I normally see when I had a test Alum rod as the Anode put into the solution (I did get bubbling when I put a different piece of alum in there... I'll have to retry). left if for a couple hours and got very mild results - the surface is slightly tinted but blotched

Was it the same alloy of aluminum? I think I saw somewhere depending on what alloy it is there may be different results or bad results. Something to think about.

Ed
 
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