Copper vs aluminum clouts for slate roof?

[ruggers]

I'm having a slate roof installed on a self build, 400 centres, and I want to know if copper clout nails should be used or aluminum?

 

The slates are 250 x 500mm 7 to 9mm thick.

 

38mm clouts required and 30mm for the eaves course.

 

Aluminum 3.35mm or the roofer says if using copper I could use 2.65mm.

 

I want the roof to last 40 yrs+ 

Some online reading says aluminum may fail between 20 and 30 years is this true?

 

We're 3 miles inland off the West coast, there's a few houses around but we do get a bit of wind in winter.

[Mr Punter]

Have you looked at stainless hooks?  Zero uplift on windy days.

[JohnMo]

We used copper. 

 

1 minute ago, Mr Punter said:

Have you looked at stainless hooks?  Zero uplift on windy days.

You don't with nails either. 

[SimonD]

10 minutes ago, Mr Punter said:

Have you looked at stainless hooks?  Zero uplift on windy days.

 

+ 1 I used these when re-roofing our old place. We had a very shallow slope so the increased uplift protection was needed.

[Redbeard]

Copper. My roof is about 135 years old. I reckon 70+% is 'as laid' and has the original copper nails. No membrane, of course, and no leaks at present.