There is provided a chromium-free coating composition for forming an insulation film, the composition having excellent corrosion resistance and excellent film adhesion and film strength after stress relief annealing (SRA), including, based on a 100 g phosphate solution having a solid content of 60% by weight, in which monoaluminum phosphate and monozinc phosphate are mixed at a 1:1 ratio: 0.5˜5 g of a solid in which cobalt hydroxide and strontium hydroxide are mixed at a 1:1 ratio: 100˜300 g of an emulsified polyester resin or an emulsified epoxy resin having a solid content of 20% by weight; 3˜10 g of aluminum silicate having a solid content of 20% by weight; and 0.1˜6 g of a titanium chelate.