Why steel becomes dark and rusty ?

Why steel becomes dark and rusty ?

im a begginer historical style blacksmith , and i still dont know how weapons and armors
are shiny and doesnt rust at all .. is it the type of the metal that you buy ? or is it a process
that should be done to the metal like heating and cooling ? i bought a few bars of steel used in cars , but its color is dark , can you help me with a method to make it shiny after forging ? or
recommend me of a kind of metal that i should buy ? any help is appreciated

Best answer:
Answer by WΘMBAT is Sparky
Long answer, or short answer?

The only reason old historical weapons stayed shiny because they were kept dry, indoors, and well-oiled. Iron + moisture + air + a few days = rust.

The short answer is you use a grinder and grind off the all the rust Then get a buffing wheel and some polishing compound, and polish the guts out of it. In the old days, the only "trick" they used was a lot of elbow grease since they didn't have power tools. There's nothing in the forging process that will make a difference, all plain carbon steels are equally prone to rust.

Note: there IS another way to prevent rust, but it's only been around since about 1900. That is, add a lot of chromium metal to the steel.......making it "stainless steel." Of course, historical blacksmiths wouldn't have had this stuff.

There is a common type of stainless called grade "440C", this makes superb cutting blades and is very common for kitchen knives. Not the best for swords though because it's too hard and brittle. Also not good for armor because of the price, and because it's tough to forge and work with in general.

For armor, for a beginner, car body panels are actually a great material. They're strong and tough, easy to shape, and easy to cut, drill, and/or weld. The steels in car bodies have quite well balanced properties.

Know better? Leave your own answer in the comments!