Only wrap steel headers you want to disintegrate. The wrap elevates the coating/steel way beyond its acceptable heat range. At these higher temps the material oxidizes (rusts), the opposite of what you want, and many IMO wrongly assume its the wrapping trapping moisture, and it also "fatigues" the metal, ie causes the metal to overly expand from the high temp, and then has to at a norm temp contract all the way back, eventually fatiguing the metal until it wants to crumple after enough cycles. Cast Iron or stainless is more conducive metal for being wrapped