Galvanized steel welds similar to uncoated carbon steel when properly prepped. If you attempt to weld galvanized steel without removing the galvanizing from the weld area, the weld puddle will pop, blow out and create a health hazard to the welder and any individuals in the immediate area.
Prepping the Galvanized Steel
Removing galvanizing from galvanized steel is best accomplished with a hard wheel, flapper wheel or grinding disc attached to a grinder. Hold the grinder at a 15-degree angle to the metal, and make long passes along the weld area with light pressure being applied to the grinder. The relatively flat angle of the grinder is to reduce the amount of carbon steel that is removed during the grinding process.
If you use a coarse grinding wheel or grinding disc, you will need to make additional passes with a finer grit flapper wheel or grinding disc to ensure that all the galvanizing is removed.
Welding Galvanized Steel
With the galvanizing removed, the carbon steel will weld just like uncoated steel, and all standard forms of welding can then be used. Standard welding prepping practices should be used to complete the prep work, for example grinding knife-edge bevels on thicker metal. If a lot of yellow-green smoke is noticed during the welding process, or floating fluffy white material is seen floating in the air, there is still galvanizing in the weld area and more grinding will be needed.
After the welding is complete and allowed to cool, put cold galvanizing over the weld to maintain the galvanized steel's rust resistance. Cold galvanizing is available as a brush-on coating and in a spray can.
Welding galvanized steel without removing the galvanize coating will result in emission of a heavy, noxious yellow-green smoke that will envelop the welder. Continuous exposure to this smoke can result in galvanize poisoning.
Galvanize poisoning symptoms include a severe headache and nausea. To reduce the effects of galvanize poison, move to fresh air and drink plenty of milk to settle your stomach. There are ventilation welding hoods that can reduce the amount of smoke the welder inhales.