On Jun 5, 11:19 am, Doug wrote:
On Jun 5, 12:14 pm, N8N wrote:

On Jun 5, 12:10 pm, Doc wrote:

When soldering copper pipe, what does the flux do to cause the solder
to get drawn into the joint? Something to do with capillary action?

If I understand it correctly, the flux chemically performs a final
cleaning of the surfaces, prevents copper oxides from forming, and
also does help draw the solder into the joint. You can even buy
what's called a "tinning flux" which contains a small amount of solder
and helps make a more reliable joint.

nate

As I understand it, nate is correct. The solder flows into the joint
because the joint is hot and it melts the solder. The heat along with
the close surfaces (capillary action I assume) causes it to draw into
the joint. You can solder without flux, but it is not recommended for
the exact reasons that nate mentions.

It also serves as a wetting agent which is what helps the capillary
action and to ensure full joint coverage.

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