Spaceframe sacrificial Mg anode

I friend recently removed some 6061 alloy sheeting from a historic racecar spaceframe and found the corrosion was significant at the point where the rivets held the sheet. In discussion I suggested that a sacrificial anode of a less noble material may help - ala marine anodes of Mg. This 3mm x 20mm x 20mm Mg anode would be held in contact with the steel/alloy with a rivet/bolt. Does this sound a reasonable precaution?

Sounds sensible. I knew a family who had an Aston Martin DB5, by the time it was 30 years old you could poke holes in the bodywork.

I have heard similar stories of classic cars with Supraleggra construction.

It works on oil rigs.

By implication, it would would on Aston Martins  

 I zinc it would help. 

 I zinc it would help. 

I saw what you did there --- Mg is light and 'racey'!

I have heard similar stories of classic cars with Supraleggra construction.

I assume you meant superleggera. It just means "superlight" in Italian. It's not actually a thing.

Will the car be operated in seawater for prolonged periods? 

No of course not. The chassis will be operated on the usual roads, but it's much easier replacing an anode in 10 years than chassis sheeting.

Is a return path required for cathodic protection to work?

Ah, I  think I get it. Unless there is something to complete the circuit between the wet bit of the frame and the anode then you'll only protect the area local to the anode.

I assume you meant superleggera. It just means "superlight" in Italian. It's not actually a thing.

it actually is... a method of bodywork construction with small steel tubes covered by alloy sheet

https://en.wikipedia...ki/Superleggera

So is Sink coating not good enough on Alu parts? I completely forgot the name of that list of metals arranged by uh.. purity/corrosion.

so an anode would need to go in each wheelwell?