Otto you hit it on the head. I was using 4043. Thanks for all the quick replies. I have much to learn and think I found the spot. Regarding the CRC brake cleaner it works well for cleaning critical parts. Let it fully evaporate and use ventilation to get the fumes out before you weld though. Arc and...

Question for you'se. Today I welded a .050 wall pipe ( machined custom) to a manifold block. Both were 6061 and just machined. I cleaned with crc brake cleaner after wire brushing with SS brush used only for aluminum. It went well but there was a whitish soot like film over the weld when done. 2% la...