Rust stains probable causes - improper surface preparation. Use of nails not protected against rusting. Failure to countersink, and apply rust inhibitive primer. Painting over rusty nail heads, in a short time the rust will bleed through again.
Nailhead rusting solutions - countersink the nails, spot prime and use acrylic caulk. Rust spots will appear if you or other rusting metals without prescribed preventative measures. Specify galvanized, aluminum or stainless steel nails.
Primers and exterior finishes - Priming and proper surface preparation are essential with a corrosion resistant primer. Ask your Muralo dealer for the best Muralo exterior paint for your project, in the color and sheen of your choice.