SS430 Wire Has Black Spots. Why?

A. Hi Harish, you haven't provided a lot of information about your wire rolls, but that looks like oxidation on it. I would be looking at how/where you stored the rolls, and look up as there is likely something dripping on them, maybe something rusty above them. Do consider that it may be condensation that is dripping on the rolls as well as a leaky roof.

A. Harish,
Given that the spots cross multiple strands of wire, I would say this is something that happened after the wire was coiled, and not due to the wire itself. Also, since there are distinct spots of varying sizes rather than a more evenly distributed staining, it looks to me like this coil was splashed with a corrosive chemical. Or perhaps even just water, since this is 430 and not very high in the stainless scale of corrosion resistance.

Though it is a possibility the spots are something other than iron oxide, depending on what chemical it was hit with.