Production method for treatment solution for forming insulating coating, production method for steel sheet having insulating coating, and production apparatus for treatment solution for forming insulating coating

A production method for a treatment solution for forming an insulating coating, the treatment solution comprising at least one of (i) phosphoric acid and (ii) a phosphate salt, and one or more particulate metal compounds, the method comprising:

• mixing a solution A comprising, on a PO43− basis, in a range of 0.20 mol/L or more and 10 mol/L or less of the at least one of (i) phosphoric acid and (ii) the phosphate salt, and comprising, on a metal basis, less than 0.50 mol/L of the one or more particulate metal compounds, and a solution B comprising, on a metal basis, in a range of 0.50 mol/L or more and 20.0 mol/L or less of the one or more particulate metal compounds, and comprising, on a PO43− basis, less than 0.20 mol/L of the at least one of (i) phosphoric acid and (ii) the phosphate salt;
• and
• stirring the mixture with a rotor-stator high-speed stirrer such that a peripheral speed of a rotor of the stirrer is 10 m/s or more while stirring the mixture within 60 seconds after starting the mixing of the solution A and the solution B.