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After hearing about the 720 rule, I decided to see how well my setup would do at trying to grow 0.001" of anodized layer. The most accurate measuring equipment I have available at the moment is a 0-1" micrometer, which can measure to the nearest 0.0001".
I started with an aluminum rod that was 0.2538" diameter, and after 60 minutes of anodizing in a 1:1 electrolyte bath at 12A/ft^2 at 61F, I dyed the part, sealed it, and measured it.
OD after anodizing is 0.2546", a growth of 0.0008" for the diameter, or 0.0004" per side.
However, assuming a TypeII anodized layer is 2/3 above the original surface, 1/3 below, this would yield an anodized layer thickness of about 0.0006".
If the layer is 50% above, 50% below the original surface, this would yield a layer thickness of about 0.0008".
So... my estimate of this layer's thickness is 0.0006"-0.0008". I'll be sending this along with some other test pieces off in the next few weeks for thickness testing with an eddy current thickness gage. We'll see how it correlates.
I started with an aluminum rod that was 0.2538" diameter, and after 60 minutes of anodizing in a 1:1 electrolyte bath at 12A/ft^2 at 61F, I dyed the part, sealed it, and measured it.
OD after anodizing is 0.2546", a growth of 0.0008" for the diameter, or 0.0004" per side.
However, assuming a TypeII anodized layer is 2/3 above the original surface, 1/3 below, this would yield an anodized layer thickness of about 0.0006".
If the layer is 50% above, 50% below the original surface, this would yield a layer thickness of about 0.0008".
So... my estimate of this layer's thickness is 0.0006"-0.0008". I'll be sending this along with some other test pieces off in the next few weeks for thickness testing with an eddy current thickness gage. We'll see how it correlates.
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