The normal alloy for this application is 6061 or 6063 T6. The 2 alloys you mentioned are about 80% as strong.

If I am looking for aluminum, my 1st choice is 7075 T6 or T651 with 6061 T6 2nd.

7075 is about 1.5 times as strong as 6061 but it is normally hard to find, is not available in all sizes and expensive. I have stumbled across some deals at surplus yards.

For any al tube you should treat the inside with a long life corrosion protection. Like Boeing Boeshield T-9 or CRC Heavy Duty Corrosion inhibitor. These look like a wax when dry. One reason highly stressed metal tubes fail so quickly in salt water is corrosion in micro surface cracks. Keep it clean.


There is a difference between suppliers and there are many grades of al tubing. Each alloy has an allowable range and the range is pretty big. The more expensive tubing has tight quality controls and is tested.

The best tubing is name brand like Reynolds. For strength it will test out at the top or even above the allowable range

Next is mill spec. Tubing sold for spinnaker poles is normally mil spec and will test out in the top 80% of the allowable range for the alloy.

Below mil spec is a big group of quality tubing. This is normally sold in big lots to manufacturers. Most dealers will just look at you blankly when you ask about it. There are a few dealers you deal with hobbyists that can help.

At the bottom is cheap generic tubing. It is probably the alloy listed and strength can be anywhere in the allowable range

If you can, I would use carbon. It is a lot more durable