What coating is this

As in the title, what the coating/finish on many of the factory engine brackets. I’ve attached a picture of the ISV bracket from my 8V GTi. Looks too dull to be passivate zinc

 

Zinc passivated usually, but would have faded away over the years.

 

Ahh okay, This was my thinking but I wasn't sure it could fade that much. How about the serrated alternator bracket thing? Zinc Phosphate maybe

 

All the same as I recall.
But I prefer the grey phosphate look myself.

 

Great! I'll check my plater can do phosphating and go for that