Aluminum Anodizing

dragos28

dragos28

Registered
Registered
Joined
May 14, 2016
Messages
54
Does anyone anodize aluminum?

If so can you tell me what I'm doing g wrong

1f5b691867ed5350ab5880d28ac38824.jpg

Process is the AL is polished, washed in degreaser, dunked in desmut then in the anodizing tank. 8 pieces at 15v 9amp 60 min
Then 30 min in dye and 30 min boiling water.

Yet they never come out consistent.

Temp of acid is 79.

Any help would be appreciated
 
Did you start with bare aluminum or aluminum that had been anodized before? If previously anodized it must first be de-anodized, another chemical process.
 
dragos28, fro some reason I am not seeing your pictures. thus I am not able to see what our are talking about on constancy.
 
I noticed that also, I see them on the mobile app but not on the desktop. I'm not sure what to do I uploaded them...
 
Anodising relies on a constant current density of around 1.5A / dm2. That means that a plate 10cm x 10cm (4 x 4 in) will have a surface area of 200cm2 (both sides excl edges) or 2dm2.
So ideally a constant current source power supply would be set at 3A
In your case, calculate the total surface area to determine your current and ensure that the cathode is larger in surface area than the part(s) and ideally surrounds your part(s).
This all assumes that acid conc etc is correct.
(My apologies if metric is not your preferred language)
Graeme
 
That looks like a constant current source in the background of your pic. Make sure it's reading current as the constant not voltage by setting a low voltage first then increasing the current to your desired value.
My guess is that you have 50mm RHS that you are anodising. Therefore your surface area per part is 200 cm2 or 2dm2 and 16dm2 for 8. This equates to 24A required! And one small cathode close to only one part.
Graeme
 
I don't have my paper in front of me but I did the total area and used the 720 rule/calculator to arrive at 15v 9a for 60min
 
If it is 50mm RHS the area of each is approx 32 sq in or 256sq in for 8. If you are using the LCD 720 system my calcs give approx 11A (in your ballpark). This should anodise albeit with a higher porosity than with a higher current density. (I prefer a higher current density unless you want deeper colour when dying).
It then comes down to a greater cathode area and closer placement.
Graeme
 
You must log in or register to reply here.
Back
Top