Zinc coated fasteners are the most basic type of coated fastener. This coating is inexpensive and not made to be used outdoors. Since the coating is inexpensive, these types of fasteners are made cheaply so they are harder to drive and they strip out more easily.
A step up from zinc coated fasteners is the electro galvanized fastener. Their galvanized coating is attached to the fastener using electricity, producing a shiny, smooth finish. These fasteners are rated for light outdoor use and should really be covered to prevent rusting.
Hot Dipped Galvanized
Hot dipped galvanized fasteners are the first grade of fastener that can be left exposed to the outside elements. They will eventually rust out and it doesn’t take long for them to leave “weeping” stains on boards. They are relatively inexpensive and are incredibly common for outdoor projects.
Ceramic coated fasteners are more expensive however, they are well worth it. They resist rusting better than other fasteners. Since they are designed with a more expensive coating, they also tend to come with more advanced drive types that make them easier to use and faster to drive.
Stainless fasteners are the king of all fasteners and they are the most expensive. If you live near the ocean, you should always use stainless fasteners outdoors due to the salt air. Stainless fasteners do last longer than other fasteners outside, regardless of where you live.