Exterior use of 6061 alloy

Hi Steve,
As a long time builder, user and owner of aluminum alloy boats perhaps you can answer this question: How does the odd bit of raw 6061, above the waterline , but on the exterior, fare visually over time in comparison to 5086? In particular, we’re building a Dix 43 Pilot House and I’m looking at using a 3″ half pipe extrusion as a rub rail down each side and it is only available in 6061. The hull plating is 5086 H116. The alternative is to buy vastly more expensive 5086 schedule 80 pipe and rip it on the table saw. I don’t mind spending when it’s justified but don’t want to waste money. We love the look and practicality of unpainted alloy, but my experience in non-salt environments with 6061 is that it can look pretty nasty after awhile. Perhaps it’s just a matter of an occasional scotchbrite rub-down.
The other place we’ll be using 6061 is for the rudder shaft . It’s a spade rudder with a 115mm diameter shaft and Jefa self aligning bearings. Appearance is not an issue here, and I think the 6061-T6 will be stronger than 5086 . Do you think corrosion could be an issue on the 6061 rudder shaft? We will have a comprehensive anode system.
Thanks so much-I love the new site format!

6061 is OK above the waterline in most applications. The 5000 series is tyically stronger in welded condition. For rudder stocks we prefer 5000 series but 6061 can be used, you just have to account for the difference in mechanical  properties when welded.

There will be some visual difference as the two alloys oxidize differently.

Posted by Steve Dashew  (May 16, 2009)

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