75 x 10 mm GI Earthing Flats. The mass of zinc coating shall, be 720 gm per sqm and average thickness shall be 100, microns for galvanised items., 75 x 10 mm GI Earthing, Flats. The mass of zinc coating shall be 720 gm per sqm., and average thickness shall be 100 microns for galvanised, items., 50 x 6 mm GI Earthing Flats. The mass of zinc, coating shall be 720 gm per sqm and average thickness, shall be 100 microns for galvanised items., 50 x 6 mm GI, Earthing Flats. The mass of zinc coating shall be 720 gm per, sqm. and average thickness shall be 100 microns for, galvanised items., 50 x 6 mm GI Earthing Flat. The mass of, zinc coating shall be 720 gm per sqm and average thickness