Originally Posted by
earlwb
Yes that is correct, as far as I can tell, that is the reason they copper coat the steel rods, to prevent corrosion.
Most of the 2 stroke engines we use along with the majority of lawn equipment, chain saws, etc. use copper plated steel rods. While this may make them less prone to corrosion, this isn't the main reason for the copper plating. These rods all use needle bearings and the outer race of the bearing is the rod surface itself. This requires the rod to have a hardened bearing surface yet it is not desirable to have the whole rod hardened. The copper plating resists the surface hardening process allowing localized hardening only where the plating is missing .... such as the bearing bores. Its really that simple.
Some (few) of our engines use aluminum rods but these require a cup style needle bearing that is pressed into the rod. You usually see these on engines that use a cantilever crankshaft. Some examples of engines using aluminum rods are Brison, FPE and most of the newer smaller gassers such as the Evolution line to mention just a few.
There are advantages and disadvantages for each type of rod and bearing type ..... I won't attempt to start that discussion here. These AGM engines are just using the most common type of connection rod so nothing new, different or unusual here.