Aluminum alloy for ocean front application? 1

[griffengm]

We have an assemly that is sometimes installed on ocean front sites. It was originally designed for inland applications using aluminized steel for most of the sheet metal parts. Due to the corrosion we see now, we are considering a change to 316SS or aluminum. The question is which aluminum alloy.
The parts are presently 16 gauge steel and there is no welding, only punching and forming. Some of the current parts are painted with a two-part epoxy but we may decide to leave all unpainted rather than deal with an aluminum painting issue.
Any suggestions?

Griffy

 

[stanweld]

It is difficult to answer your question because you have not defined the strength requirements. The 5XXX series of aluminum alloys, properly hard anodized should prove effective from a corrosion standpoint.

From my experience with hard anodized 2XXX-T6 aluminum alloys,used in window frames in coastal environments in Southern California,pitting became a big problem from an esthetic standpoint. Many were replaced.

 

[TVP]

5xxx or 6xxx aluminum alloys may be possible, depending on the exact requirements. Anodizing is a popular treatment if you do not wish to use paint.

 

[griffengm]

The parts in question would be made from .08" thick sheet and do not require great strength. Formability would be a greater issue. These are used in an electrical panel that is covered but not necessarily sealed from the weather.
It has been years since I last dealt with anodize. Any thoughts on costs, $/square inch, $ per pound, etc.?

Griffy

 

[CoryPad]

High formability, corrosion-resistant Al alloys are the 5xxx series. If this is low-volume, then you will be limited to whatever is stocked by your service center.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[mcguire]

If you use stainless, 316 is the right grade, but make sure you use a bright annealed (BA), 2B, or 2D finish. Do not use an abraded finish, such as a number 3 or 4 polish, as this will cause corrosion even with 316.