So i am rebuilding my brothers computer, and when i took his cpu cooler of which is a not branded liquid cpu cooler that came with it and the copper plate which is connected to the cpu has some green corrosion on it , im not sure if i need to replace this or if it is fine and something that comes over time. if anyone knows anything about this please give me some input , everything helps 
If a picture is needed i am more then happy to upload one

If a picture is needed i am more then happy to upload one