Neighbor wants to store his fertilizer outside. He had been told 5 gallon plastic can have a problem removing the lids. He likes the galvanized cans with lids at HD but wouldn't they eventually rust in the outside elements, but maybe it will takes years before that happens?

Just one 5 gallon container? How often will he use? Why not put it in a container like a large garbage container with a lid that seals. Or put his 5 gallon container inside the garbage container with any other materials they would use?

That is a good idea. I think they also have plastic tote with lids too

Fertilizer will eat the galvanizing. They do sell plastic buckets with screw off tops. Look on survival websites, possibly Tractor Supply.

Wonderful