Materials
How to weld galvanised steel
Quick answer
To weld galvanised steel: use flux-core or stick 6013/7018 on it, MIG if you grind the coating back, filler matched to the parent metal (same as mild steel; silicon-rich wires handle zinc slightly better), and prepare properly — grind the gal off the weld zone where you can — it's faster than fighting porosity. The key adjustment vs mild steel: slightly higher amps than bare steel for the same result.
Process and filler
Process: flux-core or stick 6013/7018 on it, MIG if you grind the coating back. Filler: same as mild steel; silicon-rich wires handle zinc slightly better. Zinc fume causes metal fume fever ('welders' flu') — ventilation or a fresh-air mask is non-negotiable under AS 1674
Preparation
Grind the gal off the weld zone where you can — it's faster than fighting porosity. Fit-up matters more than most beginners expect: a gap you can see daylight through is a gap the filler has to fill, at the cost of heat control.
Amps and approach
Set current by thickness as you would for steel, then apply the adjustment: slightly higher amps than bare steel for the same result. Run test coupons first — every galvanised steel joint tells you loudly when the parameters are wrong.