Modern Vespa

I have recently been changing out the water temperature sensor on my GTS which had stopped working.

When I opened the water pump cover to drain the coolant, I noticed these green deposits on the impeller blades which I presume is oxidisation from the copper nut? - Is this normal for a scooter which is 8 years old?

N.B. I have always used the correct, recommended coolant and there's been very little rust discolouration in the old coolant when doing changes.

Pitting from cavitation ?

That's my bet. So ignore.

Correct me if I'm wrong, but the discoloration is on both pushing, or higher pressure side of the pump impellor, as well as the low pressure side. So probably not cavitation; more likely deposition of something. I'd bet it flakes off with a brush, or comes off with something like LimeAWay (I'm NOT suggesting to do this, by the way. I'd leave it as-is.).

Either way the discoloration is very minor, so as long as you keep up with coolant changes there is no indication from that picture you have any sort of problem.

Thank you MS. I can't check now as I've buttoned everything up and put new coolant in, but the discolouration looked like some kind of deposit. Your explanation sounds feasible and at least gives me peace of mind.