Production method of galvannealed steel sheet having excellent formability and exfoliation resistance after adhesion

1. A production method of a galvannealed steel sheet, the method comprising:

performing a hot dip galvanization on a steel sheet;

performing an alloying and forming a galvannealed layer including an amount equal to or more than 0.05% and equal to or less than 0.5% of Al and an amount equal to or more than 6% and equal to or less than 12% of Fe;

performing a skin pass rolling at an elongation ratio of equal to or more than 0.3%; and

applying a treatment liquid which includes potassium permanganate and at least one kind of phosphoric acid, phosphorous acid, and hypophosphorous acid on a surface of the galvannealed layer using a roll coater having protrusions and recesses on a surface, and allowing the treatment liquid to react with the surface immediately after the application to form a mixed layer including a composite oxide of Mn, Zn, and P and an aqueous P compound, wherein

in the forming the mixed layer:

a first applied part is formed in the mixed layer using the protrusions of the roll coater; and

a second applied part is formed in the mixed layer using the recesses of the roll coater, the second applied part having an attached amount of P equal to or more than 20 mg/m 2 , a surface area of the second applied part being equal to or higher than 20% and equal to or lower than 80% of a surface area of the mixed layer.

2. The production method of a galvannealed steel sheet according to claim 1 , wherein the total size of the second applied part is adjusted by adjusting a shape of the protrusions and recesses of the roll coater and a nip pressure of the roll coater.