CHROME-FREE COATING COMPOSITIONS FOR SURFACE-TREATING STEEL SHEET INCLUDING CARBON NANOTUBE, METHODS FOR SURFACE-TREATING STEEL SHEET AND SURFACE-TREATED STEEL SHEETS USING THE SAME

摘要

A chrome-free coating composition for surface-treating a hot-dip galvanized steel sheet that includes carbon nanotubes and has excellent electric conductivity, comprising, based on the total solid weight of the composition: (a) 40 to 60 parts by weight of a water-soluble or water-borne organic resin; (b) 20 to 40 parts by weight of an inorganic metallic sol; (c) 2 to 5 parts by weight of a carbon nanotube paste including carbon nanotube (CNT); (d) 2 to 5 parts by weight of a metal oxide/phosphate-based anti-corrosion agent; (e) 5 to 15 parts by weight of an organic metal complex; (f) 3 to 7 parts by weight of a carbodimide cross-linking agent; and (g) the balance of water, ethanol or a mixture thereof. The steel sheet surface-treated with the composition may be useful to secure corrosion resistance without including a chrome component and shows its electric conductivity even when the coating composition is used at a coating amount of 1000 mg/m2 or more.