Originally Posted By: jsavino
This post was automatically imported from our archived forum.
Look at the picture again, the pipe hangers are made from two different matierals. Thats why there is rust. Flux is an acid made to etch into the copper to bond the solder and the cooper for a strong joint. The flux was never wiped off after it was soldered and after time oxidation will form on the pipe. Look at the top of the pipe. It is not in contact with the hanger.
From the back of the can of Utility Flux "Wipe off excess after soldering. Fill system with water as soon as possible to rinse away any flux residue."
Get a piece of copper pipe, wipe flux on it and put it on the shelf. In time the flux will turn green with oxidation.
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