Galvanised duct cuts

[Apple]

What is the chances of cuts in galvanised duct rusting? Got bare metal and moisture. Granted it should never condense if everything is good.

Are the cuts painted over or does everyone use the joints that go inside the duct so the cuts aren’t in the flow? 

Was looking at the Lindab safe duct for ease of getting a good seal but the duct goes into these and a cut there seems like a bad idea.

[Conor]

None. I've a load that have been sorting out in the rain for a year or more and no signs of rust.

[Gone West]

3 hours ago, Apple said:

Was looking at the Lindab safe duct for ease of getting a good seal but the duct goes into these and a cut there seems like a bad idea.

I fitted Lindab guttering, and the instructions say that the galvanising creeps back over a cut surface, as long as the metal is only cut with hand tools. If power tools are used the heat build up destroys the galvanising near the cut. We didn't have any rust showing after several years of use.