Hello Bill, using an incorrect filler metal. 4043 will turn black, 5356 won't, when anodized. Unfortunately, you are not the first one to find that out. I worked for a local company that had a similar experience. They had to remove all of the welds and re-weld them and then have the anodizing done again. Sorry, best regards, Allan
Don't feel bad, it happens all the time. I've learned, when it comes to aluminum, ask first.