MIG with stainless wire rusting

[telemetry]

In an effort to speed up from TIG, I got a roll of this http://www.wholesaleweldingsupplies.ie/index.php?route=product/product&path=37_97&product_id=1280 to try it out as this was a little too expensive to experiment with; http://www.wholesaleweldingsupplies.ie/index.php?route=product/product&path=37_97&product_id=233
Anyway it welded grand on 304 and much quicker, used just Co2 no argon mix or helium mix, wire brushed it and left out in the rain and it started to rust a bit, it will rub off with a cloth,
How do I get a weld that will not develop a rust as i a bit of railing to do and needs to be prefectly clean, could it have been the wire brush?
Thanks.

 

[Hitch]

A few things wrong there....

Starting with the wrong gas, no hope if you use the wrong consumables from the off.
Then the wire brush, I gather it was a normal steel bristled brush?

 

[langy]

Why do people insist on using CO2 for welding stainless !!!
There is enough info on this site to not get it wrong.

 

[pedrobedro]

Co2 introduces carbon into the weld which causes it to discolour, you need stainshield probably the universal grade would do for your purpose.

 

[BrokenBiker]

can pure argon be used for mig stainless welding?

 

[TechnicAl]

no
you need argon + 2.5% CO2

or argon + 1%Oxygen

pure argon welds look awful