How to Grind Galvanized Steelby C.L. Rease
The galvanized coating surrounding mild steel protects the metal from moisture, inhibiting rust. Grinding the coating from the steel prior to welding reduces the amount of zinc entering the weld. Zinc causes small cracks to form, reducing the weld's strength. Using the correct type of grinding wheel will remove the highest amounts of galvanized from the metal while keeping airborne particles of the coating to a minimum.
Secure the galvanized steel in a bench vise with the section of steel you need to grind sticking 6 in. past one edge of the vise jaws.
Attach a flapper wheel to the angle grinder.
Set up a fan to blow toward the bench vise. Leave enough room for you to work between the fan and the vise. Turn on the fan.
Hold the flapper wheel at a 10 degree angle to the steel, with your back to the fan. Start the grinder. Move it along the edge to remove the galvanized coating from the steel. Continue grinding until the dull sheen of the coating gives way to the shiny surface of the steel.
Allow the ground edge to cool for 30 minutes before handling it.