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What is a bleach test for anodized parts?

June 12, 2009

I have some 6061 Alum. parts anodized to Mil-A-8625 [link is to free spec at Defense Logistics Agency,] Type III Class 2 dyed black. The end customer has rejected the parts because it did not pass their anodize test. So what is this test? I was told that a drop of bleach was placed on the part and if it turns a different color it fails. It turned pink. I have never heard of this test or what the test is measuring or not measuring. If anyone could shine some light on this issue it would help greatly.

Mark Heatwole
Machine Shop - Plano, Texas

June 17, 2009

"Bleach" is sodium hypochlorite, alkaline, and attacks (1) aluminum (2) aluminum oxide and (3) hydrated aluminum oxide seal. It also turns black dye pink.This is no test, this is a strip.

Editor's note:    
   Mr. Probert is the
   author of
Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

June 18, 2009


There are some medical device manufacturers who specify a bleach test to qualify the seal. Their product will be exposed to a bleach solution as part of routine disinfecting.

Typically, commercial bleach is diluted 50% and applied to the anodize for 1-2 minutes without discoloring the surface. Very similar in nature to the ASTM B136-84 [link by ed. to spec at TechStreet] Test.

If your coating was not sealed, it would not pass this test.

Willie Alexander
- Colorado Springs, Colorado

June 20, 2009

If the bleach test was not listed or listed in a referred to spec, they do not have much of a leg to stand on for rejecting the parts. If you want to keep them as a customer, you should be able to negotiate a reasonable settlement for both sides.

James Watts
- Navarre, Florida

July 6, 2009

I think that dying is not allowed for your customer, if this is the case, try to became a black color using electrolytic coloring but remember to use aluminum racks and not titanium racks.

Franz R Wagner
- Blumenau SC Brazil

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