Black coating over insulation?

[rippie]

I am reassembling and noticed some black coating over yellow insulation under the bottom shelf in the bathroom cabinet. It effectively makes the top of the floor space where the converter lives. I was assuming it was sort of flame retardant to prevent the yellow stuff from catching in event of electrical fire. Concerned it could possibly be asbestos. Would foam be a good replacement or more of a fire hazard?

[rippie]

(Pictured). Sorry, most of my images turn 1/4 in the process of posting. Haven't figured out the fix yet. Anyway, does this look like a possible sideways asbestos coating?