my bad, I totally forgot about it in Spanish welding or soldering its the same word, so that was my mistake, this were welded and the weld were pretty good, and buffer on the outside on the inside it seems that it were machined after the welding so, this may be the proble, but i mage to clean an passivate this pumps heads, first i tried with a Ecolab product called lemon ez, and it clean it fine but there were some mark and some rust on the walls, so i decided to not give up and pick up a pickling gel from my local SS shop, and that made it so clean, the bad thing about it its that i need to buff some parts of the head because they got dull due the strong acid, but so far so good, i will passivate on Citric acid this night