Just be sure to do both sides of the metal or it will rust from the inside.

http://www.por15.com/

MANY PRODUCTS CLAIM TO STOP RUST; SOME ARE PAINTS, SOME ARE CONVERSION
PRODUCTS, SOME ARE RUST TREATMENTS. NONE SEEM TO REALLY STOP RUST
PERMANENTLY. WHY IS POR-15 DIFFERENT, AND WHY SHOULD I BELIEVE IT WILL WORK
ANY BETTER?
Rust is caused by moisture coming in contact with metal, which causes a
chemical action called oxidation. All paints provide a measure of protection
for a while, but since they are eventually softened and weakened by
moisture, it is only a matter of time before moisture penetrates the painted
surface and attacks the metal below. All of the so-called rust preventive
paints on the market (except POR-15) are weakened by exposure to moisture.
POR-15 is strengthened by exposure to moisture. Notice the hardness of the
POR-15 coating. It doesn't chip, crack, or peel like ordinary paints do, and
its hardness will resist the wear and tear of every day life.
Rust conversion products claim to change the chemical nature of rust and
convert it to a more stable element that won't rust again. History of the
failure of these products is well documented; most simply don't work for
more than a few months at best, and they are subject to the same chipping
and cracking that occurs with ordinary rust coatings.

POR-15 works because it chemically bonds to rusted metal and forms a rock-
hard, non-porous coating that won't crack, chip, or peel. It keeps moisture
away from metal with a coating that is strengthened by continued exposure to
moisture.