Originally Posted by
Schweinhund
It really just depends on the chromium content. For instance stainless, it's shiny because a large amount chromium is in it as well as vanadium and molybdenum in small amounts as well as boron.
The lower the chromium content, the less shiny it is. About 11% is where you start to see the chromium color in the metal, but it doesn't get really tangible until it's a bit higher.
They have plated lesser metals with chrome because chrome is incredibly hard along with corrosion and wear resistance.
4130 CroMo steel is typically between 0.8% and 1.1% chromium and between 0.15% and 0.25% molybdenum. That amount of chromium in a steel alloy does effectively
nada to provide corrosion resistance. Both elements are added to improve the strength of the resulting alloy, not for corrosion resistance.
https://matmatch.com/learn/material/4130-steel
Unless coated with a preservative or provided with some form of corrosion-resistant coating - like nickel or chromium plating, Parkerizing, or bluing - untreated bare CroMo will definitely rust.