Y
y_p_w
Not sure, but are you thinking of "electromigration"?
http://en.wikipedia.org/wiki/Electromigration
That's a key concern in metal layers forming interconnect (wires) in
integrated circuits. The problem happens more often when the current
is relatively high and the width of the interconnect is minimum width
- especially when aluminum is used. Often design rules state that
there should be a minimum width to interconnects for certain
applications, and sometimes copper is added to aluminum to reduce the
effect. Now they use copper interconnects which aren't as
susceptible.
Platinum can certainly erode due to heat. I remember the Japanese car
specialist I take my cars to used to use Bosch single platinums. They
noted that quite a few came back with the center electrode pretty much
completely eroded. Those use a thin platinum wire buried flush in the
insulator. Since then they primarily go with Denso.
My understanding about spark plug effectiveness is that with
conventional plugs (that develop a corroded finish) a newer plug with
"sharp edges is easier to fire. Eventually the material wears away
and the edges blunt. If you've seen the NGK V-Power and Denso U-
groove, they're trying to add extra edges to the center or ground
electrode. Good double platinums don't seem to need the sharp edges
to fire properly if the platinum areas are properly sized to both keep
clean and prevent erosion.