piston ring differences?

[volaredon]

I understand the difference between chrome, cast iron and moly rings.
but what is the difference between moly, plasma-moly, and phosphate coated?
as the moly is basically a coated cast iron ring to assist break in, what difference is there in "plasma-moly" vs (non) plasma?
If a ring set is listed as phosphate coated, is it some kind of "mix" of moly and phosphate or is the phosphate something different entirely?
I know that chrome is a material difference in the ring itself and often it is only related to the top ring in a ring set.
also (I think) that the moly, etc are simply coated cast iron rings. Right?

 

[my68barracuda]

Don,
Plasma is the process that is used to coat the pistons rings with the Molybdenum mix. With the plasma process the Molybdenum is melted and then deposited on the piston ring OD using a high temperature high velocity spray. The moly is porous, absorbs oil and helps prevent cylinder wall scuffing during the break in. With any reputable piston ring manufacturer, moly and plasma moly are the same thing.
Phos coating is similar to moly in that it is a porous coating that retains oil to assist with break in. Difference is the moly could be .010 to .030 thick and deposited in a channel on the ring face and phos is very thin, maybe .001 thick and would cover the entire piston ring exterior. Moly is definitely an aid during break in. Phos will help a little at break in but is really effective at preventing surface rust during part storage prior to installation.