Question Corrosion on GPU heatsink

[Techxz]

So I bought a few graphics cards second hand online and they have a lot of corrosion on the heatsink, which increased temperatures and caused the card to thermal throttle greatly.

After looking into it, apparently the corrosion can be cleaned off and should not happen again if I use an anti corrosive spray like wd-40.

My question is, if video cards were subjected to such physical conditions, which caused the heatsink to corrode how will this affect the longevity of the PCB and the GPU itself?

Would it be worthwhile to return it to the seller or shall I just keep them and clean it off?

 

[RememberThe5th]

Depends from what materials are they made, generally I think the back panel (Where are display connectors) are made up from metal?
But rest is coated PCB with aluminium and copper also the metal bracket or back panel of GPU is coated soo thats why they usually change color over time.

Aluminium and copper oxidises

Could you take a picture then upload it to image hosting site and then link it here?