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 43076
Anodizing different alum. types-causes
changes in finish
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I have been anodizing for a few yrs in a small in house shop. we
do 99% aluminum 2024 & 5052. here recently one of our jobs has
been plating an extruded angle from 6061-t6. we are plating them
using the same processes as before, but our results are totally
different. the parts do not have any streaking as read in some of the
other postings, but are a dull dark grey vs. the usual light alum
color. what are we doing wrong? or is this a normal problem?
thanks....
Martin Baker
small in house anodizer - Sweetwater, Texas
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What you are seeing is entirely normal. The anodised colour is
different because of the different alloying elements used. I think
the main thing causing a difference in your situation is the amount
of Silicon in the alloy. 2024 contains 0.15%, 5052 0.25% and 6061
0.4-0.8% Si. This difference is enough to give your 6061 anodising a
darker grey colour than you would get with the other two alloys.
John Reid
- Brisbane, Qld, Australia
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Let us know the acid purity, acid strength in grams per liter,
anodizing tempertature, anodizing current density, starting surface
finish, cathode material, surface preparation - then we will make
some suggestions.
Angle is 6061; round parts are 2021
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Acid purity – industrial
Acid strength – 15% by weight
Anodizing temp – room temp. non-heated (80-110F)
Anodizing current density- unknown - fixed
battery charger [link is to product info at Amazon] 12v
Steating surface finish- unknown (sanded finish)
Cathode material- lead
Surface preparation- sanded then washed with
lacquer thinner [link is to product info at Amazon].
Martin Baker
- Sweetwater, Texas, USA
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The 2000 material is less conductive and requires more voltage to
get the same amperage. Obviously your current density is lower on the
2024 so the color is different. You will have to control the voltage
and current accurately to get the same color. YOu can raise the acid
strength up to 16 or 17%/weight and partially get the colors closer
together, but the best way is to go get a rectifier with meters and
control.
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