Why does my package of Porter-Cable galvanized finishing nails say not to use them outside?

I bought Porter-Cable galvanized, 15 ga. finishing nails to use in laying deck boards (5/4" cedar). When I began I noticed the package says "Not for outdoor use - For interior only." What's up with that? I thought galvanized nails were exactly what you wanted for outdoor work.

Any ideas about WHY it says not to use them outdoors, and more important, do you think it would be OK to use them for this purpose despite what the package says?

Thanks!

First of all, they are not hot-dipped galvanized, they are electroplated. That's why they are not rated for exterior use. Second, galvanized screws or nails react with the acids in cedar or redwood, and will turn black. This will cause streaking. The best thing to secure your deck boards is stainless deck screws. For 5/4" boards, you will want to use 2-1/2" screws. They are expensive, but worth it.

Finish nails will never hold deck boards down. Once the sun hits them, they will pull out. I'd definitely recommend the screws.

First of all, and with all due respect I NEVER use Nails on decking, but I can't directly answer your Q. Have you asked Porter?

In one sense I want to assume that the process of power nailing, disrupts some of any galvanized coating on anything, as much as it could be disrupted on galvanized carriage bolts used to secure the framing to the posts, even just in the thread area. Anyone seeing galvanized anything, will notice that over time, areas will rust.

Steven Wolf
AKA: The Deck Doc
Just my two "sense"

They aren't acq approved. In wet applications, the metal in the greenwood causes the nail to rust. Galvanized means the nail has only been dipped once. It has to be dipped more than once to meet acq standards. Otherwise the nail will rust and break over a short time. Especially as thin as those are.

No way should you use those nails for that application. You will have to redo your work within a very short time and probably have to replace some warped lumber as well. Go with screws, you will get much longer lasting results.

I believe they will say "zinc plated" as opposed to 'galvanized'
just a thought - (nice posts on your deck questions, Don! =)