Necessary to prime extruded aluminum?

[jimbo]

I believe the tie down bars look to be extruded aluminum. Is it necessary to prime these for corrosion protection or is the extrusion process enough protection?

Don't want to add work if I don't have to.

Thanks.

Jim
RV9A
Emp completed
Wings in process

[terrykohler]

The extrusion process provides absolutely no corrosion protection. In fact, plastic deformation and subsequent grain alignment from the process imparts hardening and residual stress that may actually lower resistance. In the hope of not re-igniting "Primer Wars", I would suggest that if you're going to coat or prime anything at all, you start with the wrought or extruded parts. I believe I posted some ASTM corrosion test results on this forum some years ago from a wide sampling of RV parts. Rattle can zinc chromate worked very well in increasing salt spray life from a few hours to over 500.
Have Fun,
Terry, CFI
RV9A N323TP

[jimbo]

Thanks Terry for your reply. I am selectively priming and not familiar with aluminum manufacturing and what is more susceptible to corrosion. After posting I thought that most of the nonsheet Al. might be extruded and this might be a dumb question to post.

It's great to be able to get needed information.

Jim

[Kahuna]

Originally Posted by jimbo

I believe the tie down bars look to be extruded aluminum. Is it necessary to prime these for corrosion protection or is the extrusion process enough protection?

Don't want to add work if I don't have to.

Thanks.

Jim
RV9A
Emp completed
Wings in process

Yes..........