Aluminum Anodizing Cracks

Question

Aluminum Anodizing Cracks

Bester2 (Mechanical)

(OP)

19 Feb 07 15:36

I have just received a part that has spider cracks throughout the anodizing. Does anyone know why this may be happening?

kenvlach (Materials) · Answer 1 · 2007-02-19 16:58:17

This may be 'crazing,' commonly seen on hard anodizing. Due to ΔCTE between the aluminum substrate & the anodize (CTE of Al being 5x that of anodize).
Hard anodizing usually performed at about 32 ^oF (0 ^oC) & crazing occasionally occurs on heating to room temperature, but mostly due to dyeing, sealing or HW rinsing at elevated temperature. Most anodizers have process specs. prohibiting the used of HW rinsing for non-dyed hard anodize.

What anodizing specification, thickness, Type, Class...?

Bester2 (Mechanical) · Answer 2 · 2007-02-19 17:41:36

Thanks,

I found out that 'crazing' seems to be the culprit.

Thanks for the help

kenvlach (Materials) · Answer 3 · 2007-02-19 20:15:13

Crazing can be minimized.
Do you have any control over the process? If so, give the anodizing specifications & processing steps.

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Aluminum Anodizing Cracks