I want to replace a delaminating plywood top on a water tank with HDPE. The top is roughly 30 inches wide and 40 inches long and is screwed and sealed down.

I think the HDPE might work well, and be quite resistant to corrosion.

I had thought about Lexan for the same idea, but the cost is high, and it may be too brittle for an installation like that... would be a great way to inspect the tank though.