Science Experiment Help: What happens when you out galvanized nails in iodine?

I tried this lab twice and nothing happened. The instructions say to put a few galvanized nails or screws in to a small jar. Then add enough iodine to almost completly cover the nails. Finally let stand for 30 minutes. My lab worksheet also says that I should recored the color of the idone when first added, and after 30 minutes. This is the olny information that it says to recored so I am umeing that this means that the iodine is suposed to change colors. However, both of mine did not change colors, or change any physical properties at all. Please tell me what the mixture was suposed to do, and what i may or may not have done right in my experiment.