inexplicable anodizing behavior

Murnax

Murnax

Joined
Jan 27, 2003
Messages
1,277
I'm encountering a very weird problem when I try to anodize some pieces of Ti. I dip the piece into my bath with the voltage set at whatever my target is. Today I was just trying to get a gold color at 11 volts. The first handle worked perfectly. I dipped the piece in, and it dropped the voltage, then it stepped up until it hit 11 V and stopped. I took the piece out and it was a nice even gold color.

I then tried the other handle, and when I dip it in the voltage drops to around 5V and just stays there. So now I'm stuck with one gold handle and one unanodized handle. This also happened with another set of Ti handles I was trying to anodize, and I can't figure out why. Does anyone have any ideas why this happens, and how can I fix it? Thanks.

edit: the handles are from benchmade bali-songs, btw.
 
I can't say about Ti, but I have done some nickel plating, and know that if the solution gets contaminated, it will affect the results. The part has to be degreased beforehand and rinsed with distilled water, and everything else that comes in contact with the solution gets washed and rinsed off with distilled water beforehand too.
 
Maybe the handles are made out of 2 different types of titanium? In the future it is best to anodize both handles at the same time so they color the same. You might get slight differences by dipping them seperately.
 
Murnax
i know of what you speak !! i tried to anodize a "BAli" and got the same thing my bet is it is a 42 with cast titanium handles right ? im thinking is is C.P titanium , Comercial Pure . it can be anodized but must be etched first . the titanium that anodizes right away is probably a good alloy like 6-2-4-2. i tried this on some titanium i have and everything colored except the Cast handles .
 
I would bet they are of 2 different alloys... OR one has a stainless insert in it or something thats making the conduction rather than the Ti...

CP (commercially pure) ti annodizes wonderfully! all the way up to the upper reaches without etching so it shouldnt be that... You should be getting something, even if its just a dull bronze...

Try finding a multimeter and testing resistance across the 2, i think you will find that they are substancially different...

also try a peice of fresh scrap Ti and see what your annodizer does with it... You may have blown a rectifier or something too...

Alan Folts


alanfolts@hotmail.com
 
Thanks for the help guys. It can't be a contaminated solution or something wrong with the power supply, because right after having trouble with that particular handle I anodized the handles from a Benchmade 635 with no problems.

I know I should dip the handles together (and I did that on the 635 handles), but the bali handles are too wide to fit together on the Ti hook I made, so I need to make a new hook. After the one didn't work, though, I did dip both in together, and it exhibits the same behavior as when just the non-working one is in.

I tried testing the resistance of the pieces, but I don't place much confidence in my multimeter as it reads .8 ohms with the two leads touching, and it has no set zero option. However, it reads both handles as near 1 ohm.

This is a cast Ti 42 handle, and I'm pretty sure benchmade uses 6AL4V Ti. I removed all the screws and other non-Ti pieces from it, so it should just be Ti I'm putting in the bath.
 
To add to the confusion: anodic painting works. So I'm still really confused why this is behaving this way, but at least my handles are both the same color now.
 
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