Question Heat pipe turning black, is that corrosion ?

Maybe - sort of.

Copper does not corrode per se. It does to the point where a protective layer forms prohibiting further corrosion.

Usually more greenish than black but who knows how that copper has been alloyed for manufacturing and cooling purposes.

The black could be some form of copper patina (google as necessary) or it could be the copper reacting to some other environmental substance.

I would leave the "black alone" (do not clean/scrub etc.) and simply keep an eye on it.

If really concerned then send the photo to the laptop manufacturer. Ask for their comment.
 
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