Cough, BS, cough, cough. The pump is low enough in the cooling system that as long as you have the coolant level above 2/3 way up the radiator, there should be sufficient suction head to allow the centrifugal water pump to prime and pump just fine. This should not be a problem with the SHO.
The air bubbles just go to the high point in the system and get pumped along as the thermostat opens. They also collapse a bit as the system pressure increases. It is not air bubbles that causes the cavitation erosion. This type of erosion is usually due to cavitation found in high speed pumps with low suction head. I have even seen in on inappropriately designed or applied boat propellors.
In either case, the problem is the same. There must be sufficiently low pressure to allow the pumped fluid to vaporize and collapse. This process consumes energy and some of the material of the impeller. The SHOs beautifully machined aluminum pump casing and hardened steel impellor have never shown pitting in the dozen or so that I have seen.
Don't worry about this, just don't run the engine hard until you see a stabilized temperature behavior. It should take no more that about 15-30 minutes of operation to clear most of the air from the system. If you still see bubbles moving from the tube into the expansion bottle, the system is still purging air.
