What is the shiny structure under a metal coating? I performed a hot dip aluminizing on steel for 15 seconds. Then, after I bent the steel to remove the coating easier, the steel under was rough, shiny, and metallic, and was different from the original steel.The layer seems to be random and has bumpy structures. I can't mechanically removed the layer. I couldn't have analyze it chemically. Could I conclude that it is an intermetallic layer of Al and steel?
Likely an intermetallic , I think there are a couple different ones. I am more familiar with "spray and diffuse"  or vapor deposition ( Alon). Alonizing is very long ( > 24 hr) but gives a high integrity coating , can't remember the thickness.  As I remember the "diffuse" cycle takes a couple hours. I expect your process produced a thinner coating but still with some intermetallics.