No no no, our cranks haven't gone purple! That what you see is a process called ion nitriding. Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface. In turn, this hardens the exterior surfaces of the crankshaft including (but not limited to) surfaces such as the main and big end journals. Ion nitriding is one of the very many cogs in the machine (no pun intended) to create the best crankshafts in the world, delivered straight t

N... - Journal of Environmental & Agricultural Sciences - JEAS