ステンレス鋼の隙間腐食試験法

抄録

Study was carried out for the purpose of finding laboratory crevice corrosion test method necessary for the development of sea water resistant stainless steels. The test results obtained are as follows:
(1) Pitting potentials or immersion test in ferric chloride solution could not evaluate the corrosion resistance of stainless steels to sea water, in which crevice corrosion is prevalent on stainless steels.
(2) A new laboratory crevice corrosion test method was developed which consisted of immersing crevice test specimen in an aerated solution with 3%NaCl, 1/20 M Na₂SO₄, and activated carbon. Activated carbon was mixed into the solution with the weight ratio of 2 parts of activated carbon to 5 parts of the solution. The test results obtained by this method were correlated well with the immersion test results in sea water.
(3) The role of activated carbon on the crevice corrosion of stainless steels was to enhance the cathodic reduction of oxygen by increasing active cathodic site on the outer surface of crevice test specimen. Accordingly, the corrosion potential of stainless steel in the test solution having approximately the same pH value as that of sea water changes to the potential nobler than Vcrev. (the initiation potential for crevice corrosion), and then crevice corrosion occurs in shoter period compared with field test in sea water.