View Full Version : Copper Heat sink Turns Black!!! G751

01-04-2015, 06:56 PM
I have recently Purchased ROG G751JT(20dec), i have noticed that the heat sink which were shiny turned black.

My Laptop never left the Table & the operating environment is clean and free of any chemical, dust, smoke etc. which can cause corrosion.
According to chemistry copper turns into copper oxide(brownish-black ) when heated.
Hope this does not affect the cooling by hampering the heat exchange (copper -> air).

Did anyone faced same/similar problem?
Is this covered in warranty?

01-04-2015, 09:41 PM
can you post pictures?

01-20-2015, 03:05 PM

Sorry I was out on a Tour, here are the images, as you can see these fins were shiny and bright

Evil Hotdog
08-24-2015, 01:10 PM
I noticed the same ! It only happened on the left heatsink (when holding laptop with screen towards you)
Do other g751 owners have this too?

Edit: I mean the tube inside the left heatsink, not the fins.
when compared to the right side it has a different color: black/metallic on the left versus coppor color on the right.

08-24-2015, 02:03 PM
Well, but what about the temperatures (CPU,GPU)?
If they remained the same over time, than this is nothing to be alarmed for....

08-24-2015, 02:15 PM
mine are black too

08-24-2015, 03:39 PM
This is not unusual behaviour. Many types of copper and copper alloys change surface color when exposed to high temperatures. Their heat dissipation properties are not adversely affected. The left heatsink is more likely to change color because it has to deal with higher temperatures - the CPUs in these machines run hot and the CPU fan is smaller than the GPU one.

This is what occurs:
2Cu + O2 ---> 2CuO

Basically, an exothermic reaction that causes the copper to oxidize aka rust but more correctly known as Patina (after time) as this is not the same kind of corrosion that affects other metals. Don't worry about it, this reaction actually PROTECTS the underlying surface from further corrosion as opposed to what happens when metals such as iron rust. If you've seen the swampish/coral green stuff that builds on pewter or bronze, this is what that is - natural patina formed when the oxygen in air comes into contact with the metal - but these metals don't interact with water to "rust". (This is not entirely true, there are complex reactions happening to actually form the greenish patina, this stuff is just plain copper oxide.) However, the high temperatures accelerate the process and are what causes the darker color you see.

If you ARE worried, you can open it up and clean it one day, the oxidized layer usually comes off very easily.

08-24-2015, 03:48 PM
Don't worry about it, this reaction actually PROTECTS the underlying surface from further corrosion as opposed to what happens when metals such as iron rust.

@Edweird is correct.
https://en.wikipedia.org/wiki/Copper - read under "chemical" bold title

The question that should be asked is whether the thermal conductance of Cu that much different ( lower ) then CuO ?
Heat transfer occurs at a lower rate across materials of low thermal conductivity than across materials of high thermal conductivity
The answer is clear BIG YES. ( look here (https://books.google.co.il/books?id=DiFMPmXSsLUC&pg=SA32-PA5&lpg=SA32-PA5&dq=thermal+conductence+of+Cu+and+CuO&source=bl&ots=hAMOnuswIM&sig=XqUzPC1YH2mkZokmWiBA7d44tV8&hl=en&sa=X&redir_esc=y#v=onepage&q=thermal%20conductence%20of%20Cu%20and%20CuO&f=false) )

Inorder to "clean" that black layer - I found DIY solution(1 - look at the "best solution" link) (http://www.tomshardware.com/forum/257816-29-clean-copper-heatsink), HERE(2) (http://www.techpowerup.com/forums/threads/how-to-clean-pure-copper-heatsink.206488/), and HERE (http://www.overclock.net/t/704190/how-to-cleaning-copper-heatsinks-with-minimal-elbow-grease)

08-24-2015, 03:56 PM
Doesn't really matter either way, I doubt the layer on these is thicker than a couple of microns...
The reaction that causes copper oxide to form usually needs over 300 degrees Celsius so this
stuff is more completely surface color rather than anything functionally different.

Just because you can see it doesn't mean that it's much of anything. :]

08-24-2015, 06:33 PM
Mine aren't black in the slightest and it thermal throttled a lot. It even reached 96C. Can't post pictures yet as I RMAed it for thermal throttling.

di Valenti
08-24-2015, 10:10 PM
I haven't checked mine but I have two thoughts...

1. That there are just as many people that would want them black (like myself to look matching to the case), and if this didn't happen would be trying to DIP there heat sink or something like that to make it matt black. - lol.

2. I assume it was from the turbo-afterburner kicking in about Mach 2 when the flames shoot out the back as blue-flame heat in extreme mode... poor kitty... that was the wrong place to sit in the window sill... *oh my*... [George Takei].

Evil Hotdog
08-25-2015, 02:47 PM
alright thx guys for the comprehensive explanation :)