What turned my CPU block black?

[WonderSausage]

I've been water cooling for many years and haven't had this happen before. I just disassembled my EK Wave CPU block that had been in service for about a year, and after washing off the usual white plastiiczer residue, all of the copper has turned black.

The black coloring is very thin but won't come off easily, even with scotch-brite and Cameo copper cleaner.

It's not corrosion and there are no egregiously mixed metals in the loop, just name-brand nickel plated fittings. Oddly, the EK full-coverage GPU block was absolutely shiny clean copper with ZERO black (under the usual white plasticizer residue) although it was only in the loop half as long as the CPU block.

http://farm4.static.flickr.com/3131/3168208173_8df36c2135_b.jpg

Loop:
EK Wave CPU block
PA120.3 radiator
XSPC 5-1/4" plexi drive bay reservoir
MCP-655 pump
Tygon R3603 thick-wall (7/16" ID, 11/16" OD)
Distilled water with a few ounces of Pentosin blue (water color is only the slightest bit blue, almost clear)

Any thoughts?

[MpG]

No other additives? Nothing with Iodine in it?

[WonderSausage]

No other additives? Nothing with Iodine in it?

Nope, nothing but distilled and maybe 5% Pentosin G11.

[aspire.comptech]

Got an Apogee GTX in the loop?

[tiro_uspsss]

another WC mystery to be solved! :p: :D

[joecop120]

Black stuff on copper = copper oxide. My guess is that your block did not undergo an anticorrosion surface treatment before it was assembled.

[WonderSausage]

EK's full coverage GPU block, which was newer, didn't have the same issue so presumably EK changed something along the way...

[tiro_uspsss]

its very odd that the FC block didnt turn black.. a quick google on copper turning black shows alot of results mentioning sulfur contact :shrug: - most likely from cleaning agent.. but u said u used the same stuff on both blocks :shrug:

[WonderSausage]

WonderSausage what was the top on this WB?

Clear plexi.

[WonderSausage]

Here's a shot of the block after soaking 4 hours in distilled vinegar with occasional agitation.

Clearly it's corroded. I'm just used to green corrosion on copper and the black stuff was so smooth that it didn't look like corrosion to me.

This is quite odd, since the fittings are all nickel-plated brass, so even if the nickel plating got scratched it still shouldn't cause much galvanic corrosion.

Could it be that the machined surface was too rough/porous?

http://farm2.static.flickr.com/1096/3169927096_8ac110800a_b.jpg

[aspire.comptech]

Particulates in the loop perhaps?

[joecop120]

Water with a high concentration of dissolved oxygen can cause that. How the oxygen gets in the water...can't tell ya, but the elevated temperature of the waterblock accelerates the oxide production.

[pby5cat]

My friend FSLancer's water system EK blockes and Fuzion v2 looked like that after 4 months. He only had copper and nickle plated fittings. But we found all four of the bitspower injection molded Tees had cracked at the joint site and air was entering the system. So his blockes most likely oxidized, we just got the white crap out and put it back together.

Copper doesnt oxidize in water like aluminum, but it does in air, or oxygen to be more exact.

[MomijiTMO]

Most interesting. I'll ask some peoplez with larger brainz than me :p: