METHOD FOR MEASURING IRON CONTENT IN PLATING LAYER OF HIGH STRENGTH GALVANNEALED HIGH-P STEEL SHEET

PURPOSE:To measure iron content in a plating layer by peeling and dissolving only the part of a plating layer of a high strength galvannealed high-P steel sheet by the use of an aqueous solution of hydrochloric acid of specific concentration, containing specific amounts of ferrite dissolution inhibitor. CONSTITUTION:In a galvannealed steel sheet prepared by using a high strength steel sheet containing 0.01-0.2% P as a substrate, only the part of its plating layer is peeled off and dissolved by using a 2-8% aqueous solution of hydrochloric acid containing 0.15-0.25% ferrite dissolution inhibitor. Subsequently, iron content in the resulting peeling solution is measured. From the result of this measurement, iron content in the plating layer can be derived. By this method, the plating layer can be sufficiently dissolved and the dissolution of the ferrite part can be inhibited, by which iron content in the plating layer can be correctly measured.