This video is pretty inaccurate... Carbon adds nothing to corrosion resistance, it's all about the oxide phase you form on the surface. The formations you see as the microscope zooms in are not dendrites, they're a fracture surface. And the feature that they zoom into might or might not be pearlite, there's not way to know without either etching the surface with acid or jacking the contrast up so high in the microscope that you can see the difference in atomic weight of the two phases. Sorry to rain on everyone's parade, but I'm a Metallurgist, this is what I do for a living...