Wow, I must be the odd man out here. I actually let most of my stuff get really rusty and nasty before cleaning it. I have not cleaned my Morion in about a month and it has got rained on twice, though not very hard and it is only showing a small amount of discoloration and some spotty surface rust. My method is what one of the living history units uses on their armor and weapons to give them a period feel and to reduve maintenance. Let it rust for a while, until the rust has that nice dark patina then clean it with gun oil (do not use wd 30, it no longer has actual oil in it, only a synthentic and does not kill rust) or similiar oil. Use a wire brush or steel wool with the oil to clean the worst with, then use a rag to reaply some oil and store or wear with the oil on. This will create a layer of "dead" rust in between the air and the steel underneath that will help to protect your helmet, sword, armor, etc. I did this with my Kettle Helm and although I have not yet gotten that nice dark patina, it is not shiney raw steel anymore either. Alternatively, you can clean all the rust off and cover it in peanut oil (a thin layer) and then bake it on. Baking can be done by cooking it in a stove or closed grill, although this heat may change the metal's properties, I'm not sure, or by placing it out on a driveway or sidewalk on a couple of very hot summer days when no rain is expected. This will create a layer between the steel and the air much like paint. The peanut oil has a dark brownish color when used this way. I have not personally done this, but I know someone in the Kingdom of Lucerne who did this with his gorget and burgonet and it looks really good. I hope this is helpful to you or someone else here.
