MEASUREMENT METHOD AND MEASUREMENT DEVICE, AND CORROSION RESISTANCE TEST METHOD AND CORROSION RESISTANCE TEST APPARATUS FOR COATED METAL MATERIAL

Provided is a measurement method for measuring a size of expansion of a surface treatment film occurred in a coated metal material that includes a metal base and the surface treatment film provided on the metal base. The measurement method includes the steps of disposing a water-containing material to be in contact with the expansion and an electrode to be in contact with the water-containing material, and electrically connecting between the electrode and the metal base with an external circuit; applying, with the external circuit, a constant voltage between the electrode and the metal base, as a cathode and an anode, respectively, and measuring a current value flowing therebetween; and calculating a size of the expansion, based on the current value measured and a correlation between the current value and the size of the expansion, the correlation being determined on an exploratory basis in advance.