The present invention provides a heat-dissipating black resin composition having excellent physical properties such as heat-dissipating property, workability,
corrosion resistance,
solvent resistance,
coating adherence and gloss and being free from
chromium and used for surface treatment of a
zinc coated steel sheet, a method for treating a
zinc coated steel sheet, and a
zinc coated steel sheet treated thereby. The heat-dissipating black resin composition includes, based on 100 parts by weight of the heat-dissipating black resin composition: 10 to 60 parts by weight of a resin composition which at least one main resin and a
melamine-based curing agent are mixed in a weight ratio of 10:2-7, the main resin being selected from the group consisting of
polyester resin,
epoxy resin,
polyolefin resin,
polyurethane resin,
fluorine resin,
phenol resin, acryl resin and
polycarbonate resin; 1 to 10 parts by weight of at least one
pigment selected from the group consisting of
carbon black and carbon
nano tube; 1 to 10 parts by weight of a matting agent; and the balance of a
solvent. Also, the method for treating a steel sheet with a heat-dissipating black resin composition includes:
coating a steel sheet with the heat-dissipating black resin composition so that a thickness of a dry
coating film is in a range of 3 to 30 micrometers; and
drying the heat-dissipating black resin composition, and the steel sheet is treated according to the method. The resin-coated steel sheet includes a thin resin layer, shows excellent heat- absorbing / dissipating properties, has excellent physical properties such as
corrosion resistance, press workability, surface electrical
conductivity and
solvent resistance, and is environmental- friendly since it is free from a
chromium component.