I bought a nailer which came with some old nails that I'm going to use for a shed floor into pressure treated wood.
As you can see, they kinda look galvanized. They have that grey patina. But other than just looking at them, is there anything else I can do to try to determine if they're galvanized?
Those are galvanized. The texture says it all. Those different dark and light spots of silver all over the nail are crystals created as the zinc quickly cools in the air. Take a look at the image below and at this article by the American Galvanizer Association.
The probability is very high that they are galvanized, they have a speckled look. Uncoated iron/steel is either shiny or rusty and darker in colour. But it is possible that it may just be zinc coated, but that's more common on screws and is becoming more common with manufacturing in China. But these are liable to to be a bit old.
Testing for galvanizing can be done by a lab. A brine solution test will just tell you that it is coated with zinc, but not how it's bonded to the iron.
Laboratory Testing The only way to know for sure which coating is present is laboratory testing. Different forms of spectroscopy, for example, can take a sample of the coating in question and provide a breakdown of the materials present. A hot-dip galvanized coating may show a high zinc content near the outside of the coating with an increased iron content near the metal substrate. A zinc metallized or mechanically plated coating will contain a high zinc content through the entirety of the coating. A zinc-rich paint will also show a high zinc content, but will also contain other resins and binders typical to that system.
From galvanizeit.org
