The way I understood it was the streaks are running lengthwise on the tube? If the part is turned on a lathe, and there were streaks running around the circumference, I could definately see where an adjustment of the turning process was in order. One thing I would look at is tool sharpness, and using a lubricant or coolant to produce a free cutting action which leaves a good finish and would not tend to work harden the material. Most lathes don't have enough rpm for small diamter aluminum work, so it is doubtful in my mind excessive rpm is contributing to the problem. I turn .75" aluminum at 6,300 rpm, and would often use a higher speed if the lathe was capable of more rpm.
I suspect the DOM tube does have work hardened areas, in which case anealing like Fibergeek suggested may help. If beadblasting were an option for you, it could solve the problem. If that is not an option, it may be benefical to use a heated solution of stipper or lye which will remove aluminum from the surface. You would need to closely monitor the part to ensure it doesn't become pitted.
If your material was originally extruded, and I think it is likely, there could be some steaks of aluminum oxide in that length of stock, which is not unusual. In that case, another piece of material may solve the problem.
I have stripped a few parts with flaws which sound similar, and that removed most if not all of the defects. If you do more parts, and notice flaws, I would reccomend stripping before sealing as that works much faster and more evenly.
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