Hi,

It's all day I'm surfing the web but I can't address the following questions. What is the best between

HDP galvanized iron
Aluminium alloy 5052 or 6063
Stainless steel 304
Stainless steel 316

for use in salt-water sensitive shore applications, to avoid rust and corrosion? Which one is going to last the most? How long each one is going to last presumably before starting to be rusty and ugly?

In particular I need to choose one of those material for each of the following:

* the posts that are going to hold the weight of the awnings
* new window grates
* bolts and screws

There are many more aluminium alloys for marine conditions but those above seems to be two cited the most. The others are

en.wikipedia.org/wiki/Aluminium_alloy -> Applications -> Marine alloys
https://www.boatingmag.com/marine-accessories-aluminum-vs-stainless-steel
https://en.wikipedia.org/wiki/Stainless_steel -> Applications -> Water