The Vernon Anchor Aluminium Mesh (1 Viewer)

[Serdain]

In both my sources for the vernon anchors, it mentions that the electrode potential of aluminium is relevant, "A display and mounting system was built for the anchors which includes an aluminium mesh on
which the anchors rest. Mesh rather than solid metal allows water to drain away and aluminium was
chosen because of its electrode potential relative to the iron in the anchors."

Can someone please explain how this is relevant? The way I figure it is it's trying to say it's more reactive and as such if will rust before the iron, so that's why it was chosen, which makes sense, except that aluminium passivates. For those who don't know, the anchors are displayed outside on a block of wood, NEAR the sea but not in it. The fact that the Cl- ions could interrupt the passivating layer occurs to me... but is this really the reason?

Anyway, any clarification is appreciated, thanks

 

[deano1213]

Iron is only slightly passivating, thats why the anchors are so corroded in the first place, and why they are coated to prevent further rusting. Especially in a salty environment near the harbour they would eventually rust to nothing if they weren't protected. Thats what we have stainless steel for

 

[Serdain]

Iron is slightly passivating? since when? I said aluminium

 

[kormy]

the aluminium rusts instead of the iron. yes the iron is very corroded, but the people at the maritime museum hose it down with fresh water everyday to reduce the amount of possible corrosion due to the salty air. the reason the anchors are not inside the museum, like the endevour cannon, is because they are not considered to have as much historical value.

so yeah... the aluminium corrodes instead of the iron. the iron is coated with an epoxy paint to help prevent further corrosion. the anchors are hosed down daily with fresh water to prevent the build up of chloride ions, hence why the aluminium is mesh rather than solid.

for this elecive, it really helps to visit the maritime museum and go on one of their tours.

 

[Serdain]

The aluminium WOULD, yes, to a small degree, but the fact that it passivates means that it's far from an ideal metal for the situation. and the iron isn't corroded.. that's the point...

 

[aznspec]

The aluminium mesh does not corrode in respect to the iron. As a matter of fact, the tour lady who told us about the anchors said that the aluminium mesh was a form of cathodic protection, however as aluminium is passivating, it can not be used as a sacrificial anode. The mesh is only ued to drain any rain water that falls on it