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Process parameters that influence hardness and thickness of anodized film



I am quite new to anodising but my job responsibility has recently been widened to this.I am a beginner & require help.

I Want to HARD Anodise a spool valve with total area of 2090 sqmm A6061 - T6 condition material to get a 50 micron film with a hardness of 350HV min at 50 gm load. My sub contractor is using H2SO4 bath and aluminium wire jigs.

Pl help by providing

A. What else are the process parameters I should look for the process & what are the ideal values to be set. Currently my sub contractor uses:
1. Bath temp - 5 °C
2. Current - 2 amp per piece
3. Duration - 3~4 hrs

B. Which of the process parameters influence & in which direction
1. Hardness
2. Thickness

C. Is it possible to get a coffee brown color film without dye? If so which alloying element does that?

G. Muralidharan
steering systems - Chennai, TamilNadu, India


The temperature sounds too high. Usually the temperature should be between -2 and 0 degrees C. Your vendor also requires high voltage rectifiers--certainly at least 48 volts and preferably 75 volts. If the temperature is too high, the acid will attack the anodization too quickly, limiting the build; if the rectifiers aren't high enough voltage, you can't build a thick enough film. I haven't taken the time to "run the numbers" but 3 to 4 hours sounds quite high--perhaps necessitated by too high a temperature and too low a voltage.

I don't know how to get a brown color hard anodize without some kind of dye or post anodization process. While the part may look brown after etching, I don't think you can successfully anodize a brown part; I think you need to desmut it.

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

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