Welding Galvanized Steel Reinforcement

In order to volatilise the zinc coating and so achieve adequate weld penetration, both tack welds and load-bearing welds in galvanized steel reinforcement require greater heat input than similar welds in uncoated steel reinforcement. Manual metal arc, GMA and torch welding processes are all suitable techniques, as detailed in Australian Standard 1554 Part 3. In the case of GMA welding, the use of pure CO2 shielding gas will help weld penetration.

Comment on welding techniques is given under “Welding galvanized steel”.

Butt splice welds. In general, welds are made without changes to standard operating parameters other than reduced welding speed to achieve greater heat input. To achieve sound welds, all cracked or damaged areas on bar ends must be removed by sawing or grinding. To provide access for welding at least one bar end must be bevelled.

Lap splice welds. Welds are made satisfactorily using the welding processes listed above. A reduction in welding speed and an increase in heat input will help to volatilise the zinc coating and achieve adequate weld penetration.

For manual metal arc welding, the use of electrodes of a size and type which facilitate volatilisation of the zinc coating will minimise the possibility of weld porosity and liquid metal embrittlement. Cellulose-coated electrodes have given good results. Procedure testing may be helpful.

Alternatively, the galvanized coating may be removed prior to welding by using an oxy-fuel gas flame, or by grit blasting or grinding.

For all welding processes, attention should be given to ventilation or fume extraction to minimise zinc oxide fume in the welder’s breathing zone.