The silver bearing solder that I planned to use to join my shop air copper pipe uses zinc chloride for a flux. Zinc chloride is a mild Lewis acid... according to the net. Acid flux is not recommended for copper air line usually. Should I change solders? This is a low temp (good), high strength (good) solder, and I have an ample supply.
Btw, the flux is very water soluble, but I hate to put water through new lines that haven't even had air yet!
Just kidding... but I don't know if that would help.
David