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topic 4736

Can't get part to anodize!


(2000)

Q. Can someone please help. I've got the book "Artists Anodizing Aluminum: the Sulfuric Acid Process" [link is to info about book on Amazon] and followed the steps to exactly to anodize. EVERY time I try, the aluminum doesn't anodize. After the anodizing bath the part still conducts electricity, and the dye won't stick at all. What am I doing Wrong? Also sometimes the part comes out of the anodizing bath black like its covered in smut, what's up with that?

Thanx,

Chris

Chris Francis
Hampton Virginia


(2000)

? Sure you have the polarity right?

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2000)

Q. Thanks but I'm quite sure the polarity is correct. If I switch it Nothing at all happens -- no bubbles. It seems like everything is going okay but the metal just doesn't anodize. Isn't the bubbling a sign that it's working? And any ideas about the smutty stuff.

Chris Francis [returning]
Hampton Virginia


(2000)

A. I don't have that book so I don't know whether you are following the instructions correctly, nor whether they are right or wrong. But the work must be the anode, and reading between the lines I still feel it's possible you have the polarity reversed.

The most obvious bubbles are hydrogen at the cathode. If there are also bubbles at the other pole, they are oxygen bubbles at the anode. Water is H20 so you will always have at least twice as much hydrogen as oxygen.

If the bubbling on your workpiece exceeds the bubbling on the other pole, and if the bubbling is fairly well distributed, it's probably hydrogen and the polarity is reversed. If there is more gassing at the other pole than on your work the polarity is correct, but....

Organic contamination will lead to release of oxygen at the anode; it's possible the parts aren't really clean.

I don't know if you are applying enough voltage, nor whether your acid is strong enough to attack the aluminum and create the porosity necessary for dye absorption. What kind of amperage and voltage readings are you getting and what is the surface area of your part?

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2000)

Q. Hi, Thanks for the previous help but one last question. I've got the book "Artists Anodizing Aluminum: the Sulfuric Acid Process" [link is to info about book on Amazon] and all my parts anodize great now. My question is how do I achieve a Gloss or semi-gloss finish after sealing. The parts look great as far as color goes but always have a matte finish. Do I need to clear lacquer everything? Thanx Chris

Chris Francis [returning]
- Hampton Virginia


May 20, 2009

A. Hello again, Chris. The parts will be no shinier, and actually a little less shiny, after anodizing them than before. If you want a bright finish you must polish/buff the parts before you anodize them. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



September 17, 2012

Q. I'm having an issue with Anodizing also. I have a Mastech HY3030EX 0-30v 0-30A power supply. I'm using a large aluminum heat sink at my negative electrode so the surface area is as big as my work piece. My acid is battery filler (1 part) mixed with water (3 parts). I didn't have DI water handy so I used filtered water for now. When I set up my power supply for "Constant Current" (1.5A for the 37.44 square inch part) the Voltage starts at 4.8v then over an hour drops to 1.0v and I get black spots and pits on the aluminum and a minimal oxide layer (so very little dye takes). If I set the supply to constant voltage (15V) the amperage takes off. I have actual anodizing dye and Nickel Acetate for sealing... I'm almost certain it's the power supply that's kicking my butt, but not sure how to remedy it.

Richard Dubey
- Torrington, Connecticut USA


probert book
Aluminum How-To

by Robert Probert
$89 New
The Chromating - Anodizing - Hardcoating Handbook

September 18, 2012

A. Hi Richard.

- Don't start at 15 volts; you'll burn the parts before you've even started.
- Your 1.5 A is low by a factor of about 2. Figure 12 amps per square foot.
- Most heat sinks are anodized and thus not conductive.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


September 18, 2012

Q. The heat sink might have been clear anodized, I let it sit in Sodium Hydroxide till it was bubbling well. I don't actually "start" at 15v. I set the supply to 1.5A (although I hear varying amounts for ASF, a lot of 720 calculators say 6 ASF). But the supply is set to be locked at 1.5A (maybe should be 3A) and when I hook up the part, the voltage (which is floating) starts at 4.8v then by the time an hour is up goes down to 1.0v.

Should I put a power resistor into the circuit to increase the resistance in work circuit to get the circuit Voltage up to 12-15v? I figure (at 1.5A or 6 ASF) my resistance is around 3.5 ohms (if I'm reading 4.8v at start). So to get the system voltage up to 15v I'd have to add 6.5 ohms more.
does this make sense?

Richard Dubey [returning]
- Torrington, Connecticut USA


September 18, 2012

A. Hi. External resistors should not be necessary, and seem to add a complication. It may simply be that your power supply is defective, as there should be no reason for the voltage to decrease over time; it should be rising, not dropping.

When you start, the resistance is very low. That's why the voltage must be limited (which you are indirectly doing by limiting the current). As the anodized film builds, the resistance increases, and the voltage should be automatically increasing to try to maintain constant current.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



Aluminum 3003 is not anodizing

September 12, 2015

Q. I attempted my first anodizing today. My work piece was a polished aluminum 3003 ring. The wire used to suspend the piece into the acid bath was a thin strip of aluminum 6061 (all I had available at the time). After dying, the wire holding the piece dyed nicely. The work I wanted to dye, only came out with what looked like a light white coating. I'm sure I had good contact between the two. Was this the result of using different alloys? The cathode was 6061.

Michael Krauss
Hobbyist, jeweler - warminster, Pennsylvania, USA


September 2015

A. Hi Michael. It's obviously difficult to say what someone has done wrong on their first attempt in a multiple-step process, based simply on it not having worked. But I'd say that the wire material might be the first issue to address; see if you can get some 2024.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


September 16, 2015

Hi Michael,

Ted may be right, but 6061 sounds a reasonable racking material to me.

Check that your connection from rack to work is good and firm. If there is a momentary loss of contact, the point of contact on the rack will become anodised and will not continue to conduct current when mechanical contact is remade.

Harry

harry_parkes
Harry Parkes
- Birmingham, UK



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