Peteinjp

It seems the coating on the timing chain boxes holds up much better than the valve covers etc. Any idea what it is? Zinc phosphate? It does not seem like paint.

Pete

lateforlunch

I believe its referred to as "chromate"

cobalt

There are many chemical conversions used on magnesium. They are usually called acid pickles, Dow treatments and or Sodium Dichromate baths. I have used many but I believe this might be a galvanic black anodizing since the standard Dow treatments don't usually hold up as long as these seem to. Most of the treatments are designed to be used as preservation prior to painting. What is used is also dependent on what alloy and temper they are made form.

If you find out what was used please let us know.