Aluminum Temper and How it Affects Anodizing

Date 03-07-2013 12:00

Guys,
I ran into a snag with some 5052 aluminum plates we had clear anodized.
After anodizing they came out two different tints, they were both clear anodized per M12C22A31.

I have multiple parts that had this happen. I saw the delivery of the first batch of plate so I know both of these pieces are the same heat/lot#. I'm being told the "Temper" can also effect the anodizing and it's color. This material is from the same coil per the supplier.
Is it possible that different sheets can end up a different temper even if they are cut from the same coil?

I'm not that familier with tempering and the manufacturing process of aluminum sheets.

I know its not contamination from the anodizing bath. Look at the darker/ yellower colored plate and look at the tab welded on the end- its silver not yellow. That tells the anodizer and myself it's not his bath or the tab would be yellowish as well.
I know the z-clips and the tabs welded on are a different heat# than the plate itself so I'm not worreid about that. It's when these are install side by side with the smooth face side showing outward that's the problem.

Any thoughts or input would be apreciated.
Thanks
Chris

Attachment: 101_4040.jpg (690k)

By DaveBoyer (*****)

Date 03-08-2013 02:13

I am pretty sure 5052 or any 5xxx aluminum isn't "tempered", meaning heat treated.

As I understand it, color in color anodised parts is a dye treatment of the aluminum done before a clear anodise finish.

Perhaps material preparation is to bleme?

Might the yellowish cast have come from a contaminated wash process?

By eekpod

Date 03-08-2013 11:30

I thought that as well but the yellowish plate has a tab welded on the end and it is silver not yellow so that throws out that theory.
Yes colored anodizing has a dye in it, but not clear, and all my parts were run in clear.

By fschweighardt (***)

Date 03-08-2013 12:53

•The 5xxx Series alloys are high purity aluminum with magnesium added. Alloys of this series are work-hardened (non-heat-treatable) and have good formability. Alloys 5252, 5457, and 5657 are low in iron and have good luster for chemically brightened finishes. These alloys are used largely in automotive and appliance trim applications. Alloy 5052, while higher in iron, chrome, and magnesium, is a high-strength alloy and is used in structural applications such as truck panels. Alloy 5005 is higher in iron and silicon than 5052. It is a good general-purpose architectural sheet and plate alloy. Alloy 5052 anodizes yellowish in thicker coatings, while 5005 anodizes clear silver, gray, or brownish.

By DaveBoyer (*****)

Date 03-09-2013 03:18 Edited 03-09-2013 03:20

Were the parts anodised before or after the welding was done ?

Are You sure the silver looking tab went through the same process as the other parts?

Are You sure the silver looking tab is the same alloy as the other parts?

Perhaps fschweighardt has something with the comment on yellowing in thicker coatings.

By eekpod

Date 03-11-2013 10:51

Everything was welded before anodizing.
I know the tab may not have been the same heat as the plate itself.
Yes everything went into the same bath and process.

These parts are being evaluated by the Architect now, I'll keep you posted.