Copper Oxide? Help me get rid of this.

[Captain H.N.]

I tried to clean a waterblock that was oxided (brown-black) with ketchup.
The dark goes away, but now copper its opaque and its pinky-reddish, and I think its not the right look for the copper.
It should be soft pink, and it should shine.
The same thing would happen If i was using vinegar + salt, I think.

I dont want to use again that Sidol "amonia based" product to make it shine.
What can I use?

At this point you shouldn't try anything else. Oxidation strips copper from the base (it has to come from somewhere for the reaction to occur), and you can't get that shine back. Any more attempts will only be detrimental; if you really want the shine back, replace the whole block.

In the future, use 1:2 diluted hydrochloric acid to clean oxide off. It will NOT eat at copper metal, but it will eat away that brown/black crap left behind.