US 12,066,374 B2
Measurement method and measurement device, and corrosion resistance test method and corrosion resistance test apparatus for coated metal material
Teruaki Asada, Hiroshima (JP); Katsunobu Sasaki, Hiroshima (JP); and Tsutomu Shigenaga, Hiroshima (JP)
Assigned to MAZDA MOTOR CORPORATION, Hiroshima (JP)
Filed by MAZDA MOTOR CORPORATION, Hiroshima (JP)
Filed on Jun. 14, 2021, as Appl. No. 17/346,868.
Claims priority of application No. 2020-107341 (JP), filed on Jun. 22, 2020.
Prior Publication US 2021/0396649 A1, Dec. 23, 2021
Int. Cl. G01N 17/02 (2006.01); G01N 17/00 (2006.01); G01N 27/49 (2006.01)
CPC G01N 17/02 (2013.01) [G01N 17/006 (2013.01); G01N 27/49 (2013.01)] 11 Claims
OG exemplary drawing
 
1. A measurement method for measuring a size of a damaged portion formed in a coated metal material that includes a metal base and a surface treatment film provided on the metal base, and reaching the metal base through the surface treatment film, the measurement method comprising the steps of:
disposing a water-containing material to be in contact with the damaged portion 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 DC voltage between the electrode and the metal base as a cathode and an anode, respectively, and detecting a current value flowing therebetween; and
calculating a size of the damaged portion, based on the current value detected and a correlation between the current value and the size of the damaged portion, the correlation being determined on an exploratory basis in advance, wherein
the current value detected is the lowest current value during a period from 2 minutes to a predetermined time after the start of the application of the constant DC voltage.