Where the
world gathers for metal finishing
Q&As since 1989


-----

Black dye fading -- will hard anodizing help?

October 13, 2010

Dear sir,

At present we are doing room temp anodising with cold sealing. But we have problem from one of our customers that black colour fades and looks like brass yellowish colour.
Thickness we plate is 15 -18 micron.

So we are going for Hard anodising. Can you brief me about what is difference between hard anodising and regular anodising in terms of lookwise, quality, salt spray test. We require black colour as final finish. After plating is there any test to differentiate between regular and hard anodising.

What is cost wise difference between the anodising?

Thanks,

K.M.Bhatt.

Kamlesh Bhatt
Manager Plating - PUNE, MAHARASTRA, India

---

Basically, hard anodizing is anodizing that is 3x as thick as what you are presently supplying; to achieve it you need much higher voltage rectifiers, an expensive high quality refrigeration system, and better quality control. Please take this in a good spirit, cousin Kamlesh, but switching to a more difficult technology because you have not been able to properly implement the easier technology is never the right answer. Rather, you must determine what is wrong with your anodizing, dyeing, or sealing that is allowing the black color to fade so readily. A good quality black color and good salt spray resistance should be obtainable with your current 15 to 18 micron thickness, lightfast dye, and proper sealing.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
October 13, 2010

---

Check with your vendor on how colorfast your dye is. There are ratings that are standard for each dye. Check with another vendor to see if they have something that is more colorfast. Typically, it will be a metal based dye and not a pure organic.
I have never heard of a room temp seal that would compete with a proper high temp seal.
The seal is as critical as the dye.

James Watts
- Navarre, Florida
October 14, 2010