This is why anodizing can be tricky

admin

5052 aluminum MIG welded with 5356 wire.  Weld was ground off and DA'd.  Tiny holes created leaching after part was anodized.  Sent back for repair.  Repaired with 4043 TIG (dark purple/black marks).  My fault.  Didn't control process tightly enough.  Lesson learned.  I thought I would show you guys so you didn't make the same mistake.  I thought it was interesting.  Try to match the base metal with the filler metal as closely as possible when anodizing and in any case.  If you can't get a match use the same series of aluminum (i.e.  5000 series base metal....Use 5000 series filler material)  There are charts online that tell you what color certain series of aluminum anodize.  Does anyone else have any anodizing tips so we can all learn something?
Reply:Hello jef 1, I had heard that if an anodizer alters their procedure for anodizing that even 5052 that is welded with 5356 fillers can show a color variance. One of the folks over on the AWS forum had some parts that had a match problem. When they looked into the issue further they found that the acid soak of the parts was longer than it should have been and it overly etched the area adjacent to the weld metal prior to the completion of the anodizing process and a color difference was the result. Nice post and thanks for sharing your experience. A shop that I had worked in years ago did an aluminum handrail job for a local company and wasn't aware of the 4043 and anodizing issue. The entire job had to be done over due to the "black" welds that showed up when the rails were clear anodized. Best regards, Allanaevald