Experiment Cu: vinegar, vinegar + salt, solvent

[RubberDuck]

Vinegar is no longer used to clean anything,

According to --> MaxxxRacer's Water Cooling Guide: The basics An Introduction to Watercooling your Computer <--

1. Flush the radiator with distilled water. I suggest getting 2-3 2.5gallon jugs and just start pouring about 2.5-3gallons of distilled through the rad.
2. Pour Distilled or De-Ionized water into radiator. - Pour until full, drain and repeat. Shaking the radiator when it is half full of water will help. Repeat this 3-5 times.
3. Following the same procedure as in step 2, repeat with vinegar.
4. Fill the radiator with vinegar, and let it sit for appx. 1 hour.
5.Flush the radiator, following the procedure of step 2. Repeat Step 3 as well.
6.Repeat Step 4.
7.Repeat Step 2.

Also says

I have updated the guide to limit the soaking of components in vinegar for no more than one hour. A tale-tale sign that vinegar is eating your copper components is a blue tinge to the vinegar, which is caused by copper ions being dissolved into the vinegar.