I got this from Clevite:The 4th coating on on a trimetal bearing is for storage. called a flash plating.
FLASH PLATING - Most trimetal bearings use what is called a “flash plating”. This is an: extremely thin layer (approx. .000030’) applied all over to provide uniform appearance and protection from rust and oxidation in storage. The common flash platings are either an alloy of lead and tin ranging from 10 to 20% tin content or pure tin. Pure tin has a more whitish color while the lead-tin alloys are a medium gray color. Both have a satin finish.
This is what mousefink was talking about "sliding layer" earlier! I mentioned a slide coat as we called it many years ago! I guess its called "flash plating" now. The 4th plating on on a trimetal bearing is for storage.
Last edited by painted jester; 12-12-2012 at 12:52 AM.