Aluminium passivation - for aluminium to be used outside

[birchy]

Have you got extremely salty rain where you live? The fence posts down one side of our garden are made from 2" diameter aluminium tubes. I'm assuming they are ex scaffolding poles. They're not anodised or otherwise protected. They've been there for over 30 years and show no signs of corrosion or pitting, etc...

[CHudson]

Thats good to know. Dont have any salty rain or anything but I intend on selling these parts so I need to ensure there suitable for purpose etc