PURPOSE: To inspect the corrosion quickly, easily and non-destructively by measuring a planar distribution and an absolute value of a polarizing current by giving a lower potential than a corrosion potential of a material to the surface of a material, with regard to a sticking quantity and a distributing state of a CaCO3 matter sediment sticking to the surface of an apparatus placed in the sea water.

CONSTITUTION: A cell which has contained an opposed pole 1, calomel electrode 2 and a 3% NaCl solution 6 in the inside of a holder 3, and has installed a sealing material 4 made of silicone rubber to the tip of the holder 3 so as to contact to a sample softly and exactly is placed on the surface of an apparatus placed in the sea water. Lead wires of the sample 5, the opposed pole 1 and the calomel electrode 2 are connected to a potentiostud device, and with respect to the corrosion potential of the sample, a cathode current in -100W400mV is measured. The cathode current corresponds well to a grain boundary corrosion generating position of the sample 5, and also decreases by the corrosion depth. In this way, the inspection can be executed quickly, easily and non-destructively without measuring a sticking quantity and a distribution of a CaCO3 sediment of the corrosion position.