Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Aluminum components are getting puncture holes during anodising
Q. We have a dyed component for anodising; we tried with normal continuous current but the surface got "punctured", but we did it with pulse and we got the result. But the process is still not established. Can anyone suggest a tried process which works 100% for dyed components, as the client wants the component to be dyed in black .
Nagendra Suryasmall scale jobworks - Bangalore, India
April 17, 2009
Treatment &
Finishing of
Aluminium and
Its Alloys"
by Wernick, Pinner
& Sheasby
(note: this book is two volumes)
on eBay or
AbeBooks
or Amazon
(affil links)
A. Hi, Nagendra. May we take it that your shop is experienced in electroplating but is new to anodizing? Anodizing is an electrically insulating coating. So when you begin the process you must start at very low voltage (or at a controlled current) or you will burn and puncture the aluminum. As the thickness builds and the electrical resistance rises, you must raise the voltage (or maintain the current) because it starts gradually becoming a better and better insulator.
So, in addition to obtaining some books about anodizing to get a deeper understanding, you will need to buy rectifiers that offer ramp control for anodizing. Good luck. And you need good contacts on your racks because if a contact is poor and broken when the voltage is low, and then conducts when the voltage goes high, you will burn the parts. Best of luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 17, 2009
A. Ramp control is a lot more foolproof than an employee and will save a lot of problems in the long run. Some companies can retrofit some of the power supplies.
Pits can occur in the rinse tank and the dye tank in some cases. You need a book to cover the why's and the preventions as it is more than a 1 paragraph answer.
So, you need to know when the pit is occurring.
- Navarre, Florida
April 21, 2009
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