I built my headers out of 16 g 321 ss. Really needed no coating. Someone sold me on the idea of keeping under hood temps lower with the cer black. Said it was good for 2000 degrees.
First time on the trans brake cooked the finish. After that, anywhere you touched them, the coating would come off like dust.
My single egt probe would get to approx 1700 on the brake.

e-mail sized pics 069.jpg
"use it 'till it breaks, replace as needed"