Thermostat housing/bend

[Doug G]

Why? You're not using seawater as coolant are you? The thermostat housings are cheap, so that its not too painful to replace them every 10-20 years.

Tim

This one has lasted less than 5 years.

It's possible that the water that you are mixing with your coolant has a very high or very low pH and that'll do it for sure.

That's a consideration.

[Tim]

Using plain water rather than a water/coolant mix will speed it up too. I have to admit that for many years I just used tap water, but coolant does keep the rust out of it much longer (or maybe the bright green dye just makes it harder to notice).

Tim

[Doug G]

I will replace the tap water with coolant.