Copper Oxide? Help me get rid of this.

[Waterlogged]

Hi Waterlogged, thanks for your reply and interest for the problem.
I agree with you, radiators are hard to clean and rinse at 100%, 'cos of the internal structure.
Actually its hard for me to find an alternative to acids, vinegar and so on.
If im not wrong, copper its cleanable only with acids or alkaline liquids.
What should I try?

I think hot deionized-distilled will be ok, but no so efficient in removing oxide.
Using other kind of chemicals products may cause other collateral effects, I dont know.

May I have to dilute vinegar, acids in more water, so they will not be too aggressive on copper.
Btw, I think the main problem was cause by some rests of Sidol, alkali metal polish.
The water used for about 4-5 months initially, when I rebuilt my watercooling rig on October 2009, its a bit too acid, and I guess it's not so deionized as the label "say".

This time I will not use the Sidol, more diluted vinegar or hydrocloridric acid.

And guess what, I bought 1 liter of BIDISTILLED WATER.
Never tought I would need it ever.

The reason for washing with vinegar was back in the pre RoHS days, the flux that they would use to help solder the rads would stay inside the rad and contaminate the water. Since all new rads must now be RoHS compliant, they use a water based flux that washes out with simple hot water. Continually using some form of acid to clean your rad is just further etching it and making it thinner and thinner. It was clean with the first washing, stop using caustics to clean it and your problem will go away. This is similar to an old, somewhat common problem we saw from pre RoHS Thermochill PA users that would always dump out rinse water with a blue tinge to it because they allowed the vinegar to sit in the rad for too long, this would cause them to think the rad still wasn't clean so they dumped in more vinegar and got into a repetitive cleaning loop that never allowed them to get clean water to come out of the rad.

Could be that there are some metals inside radiator, when u think at it if fitting that are in direct contact to another metal will run higher risk of galvanic corrosion when mix metals. Maybe check what metals are on radiator ?

This isn't galvanic corrosion, it's acid erosion.