Platinum spark plugs?

Not sure, but are you thinking of "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.