Re: New + Confused
I haven't had one of these engines totally apart yet...But...
I would guess that the process of making the rod would involve a case hardenable material such as ANSI 8620 or some hong kong phooey eqivalent.
You don't want the entire rod hardened, only the areas that will accept bearings.
In this case the areas to be left "soft" are copper coated...which may give the appearance of rust or "bronze" especially after heat treating.
In a case hardening process, a very tough material is used for the core of the part...Carbon is introduced to create the case hardening...usually .015-.040 deep.
The carbon wll not leach into the copper coat. This way you have a part that is hard where it needs to be...the big & small ends and tough through the beam.
Again talking off the cuff about what would be standard for a steel rod...so don't quote me on this one...but I would be willing to bet this is the case.