Hi
@Pyrenees
The way it looks in your first picture, it's either algae or I think it's more like "verdigris" due to a reaction of copper in the expansion tank. Unfortunately, this container cannot be opened without destroying it.
Cleaning the bottom of the radiator from your second picture is rather unprofitable because it looks like the nickel layer has come off. Cleaning would only help a little in the short term, but it can still happen that the nickel layer further decomposes or peels off and thus either further damages the circuit or it even ends up leaking.
Unfortunately, I can't tell you why the two retaining screws of the DC-LT pump are rusting.
You are welcome to contact the support (
info@alphacool.com), it is best to link this post to it.
Best Regards