[smiller]

A question for the alclad/chemistry experts!

My understanding of alclad is that the thin layer of pure aluminum on the surface oxidizes rather quickly (within a few hours?), which actually protects the aluminum from further oxidation.

I scruffed up (with maroon ScotchBrite pads) a bunch of alclad fuel tank parts in prep for tank sealant, then didn't get to the sealant part. Now a year (!) has passed. Looking at the parts, they still look scruffed up and "ready to go." (I had covered the parts so they're not even dusty.) I was thinking of wiping them down with a solvent such as MEK and resuming the job. But I can't help but wonder: will that get the protective layer of oxidation off so that the sealant will bond well? Or do I need to re-scruff? (No biggy, but I don't need "make-work.")

 

[az_gila]

At this point an acid etch might be the best thing before assembly. You should already have some "tooth" in the surface and the acid etch will remove any minor corrosion.

 

[airguy]

Removing the oxide layer doesn't do anything to help the bonding, Proseal will bond to either the raw elemental aluminum or the aluminum oxide. The reason we scuff it first is to roughen the surface and increase the surface area (think about all the microscopic scratches, much more surface area now, can be as much as 20X more) to give the Proseal more surface to grab onto so it doesn't peel away. A wipedown with MEK is more critical to make sure any surface oils are gone and let the Proseal have intimate contact with the surface.