I need to relay all the tiles on my side slate roof, its a semi detached house. I live fairly close to the sea so I wonder what type of nails I will need for the slates. Seems I can use Stainless, Copper or Aluminum. Galvanized has been used and this is where I have the problem, they have just corroded away due to salt air. Which type of nail would you experienced roofers recommend and what length please?