discoloration after anodizing aluminum

Date 01-19-2015 13:38

I’m having problems with my welded parts after anodizing. It doesn’t happen on all of the parts the frequency is minimal, but when it does happen it is a big headache.
Does anyone have an idea what is causing the discoloration? It looks to mostly at the edge of the arc cleaning etched area.
Info 6063 Aluminum extrusion welded AC GTAW with 5356 filler using a helium argon mixed gas anodized after welding.

Attachment: DSC00564.JPG (768k)

By Lawrence (*****)

Date 01-19-2015 15:40

Frank Armao says even with the correct filler (which it appears you are using) that sometimes color match issues can come about on base metals and weld metals due to aggressive acid etching during the anodize process.
http://www.thefabricator.com/article/aluminumwelding/aluminum-workshop-matching-colors-after-anodizing

As a bonus for others who may be reading this:
http://www.thefabricator.com/author/frank-armao?page=1

Here is a body of Frank's work collected in "The Fabricator"

Some real eye openers folks... Especially for those of you who still preheat aluminum before welding.

By Mwccwi

Date 01-21-2015 15:14

Thanks, that confirms a thought that I had. In the I had probled of spot marks we called peppering and when we got together with our anodizer and lessend the etch time the pepper went away, I recall seeing that (shadow) in a similar location with the peppering. After seeing your suggestion I looked into the issues and discovered that our engineering team is adjusting anodize variable to increase coating thickness.

By supermoto (***)

Date 01-30-2015 12:48

It's been a while since welding aluminum and we used 4043 and 5356 mostly. Doesn't one have a better "color" match than the other. I can't remember, but if it were being flushed one was used to make sure it wouldn't show the welded joint after anodizing.

By aevald

Date 01-30-2015 15:23

Yes supermoto, and the 5356 is suggested for better color match, especially when the base metal is 6061 and will be anodized. Best regards, Allan