Regardless how a piece of steel is treated, if left outside in a moist environment it will eventually start to rust at some point in time. I use a four step process to mitigate the rust problems which seems to work quite well. In fact I have left several pieces outside since early spring (remember all the rain?), and they only have a very few spots that have started to show any signs of surface rust. This only has happened in places where I have not been able to get a good coat of paint inside of a tight joint or weld. The steps I perform are as follows:
In addition I would recommend these tips:
If you notice any rust then clean it off with a small wire brush and spray the area with Rustoleum Rust Reformer. This will cause the remaining surface rust to convert into a paintable black surface. After 24 hours you can paint the affected area or just leave it alone if it is not too noticeable. Many people including myself feel that a little rust on a patio or lawn decoration actually enhances the look of the artwork. All it takes is minimal care to keep your purchase looking nice and it will last for many years. If you are not willing or able to clean the occasional surface rust and would like me to do it for you that can be arranged as well. If it is a minor area I would likely clean it free of charge, but if you have a piece that has been neglected and shows significant rust then there will be a reasonable fee.
If you have any questions, then please don't hesitate to contact me via my Contact Page.