Electrochemical measurements on hydrogen entry and permeation through metallic materials were reviewed focusing on its basic concepts, derivation of hydrogen diffusivity from experimental permeation current. Some examples of modified Devanathan's method to apply corrosion test are demonstrated.
Permeation of anions into a passive film of iron was investigated by X-ray photoelectron spectroscopy of a passivated Fe surface previously immersed in an anion solution for the time before breakdown occurred. Hard base anions like CH3CO2－ and F－ were impermeable into the passive film, leading to difficulty in passive film breakdown. However, I－ belonging to soft base anions and SCN－ to soft and hard base anions penetrated into the film. It was believed that I－ inhibits and SCN－ stimulates the anodic process of iron corrosion in an acid solution within a tiny metastable pit forming before breakdown, resulting in suppression and acceleration of passive film breakdown, respectively.
Phenolic resin modified by Mannich reaction with an amine was investigated as an alternative to chromate on galvanized steel surface. The corrosion resistance of the resin coating was improved with increasing of the curing temperature, furthermore also improved by addition of phosphoric acid into the resin solution. Surface free energy measurement, infrared absorption analysis, GDS analysis, XPS analysis, etc. were carried out in order to clarify the effect of curing temperature and the addition of phosphoric acid; as the result some findings were obtained. The coating film became more hydrophobic, because cross-linking reaction proceeded with the elimination of the diethanolamine, which is the amine for modification, in curing over 160℃. It was revealed that the phosphoric acid included in the resin coating has been eliminated together with diethanolamine during the cross-linking reaction and it has diffused through the resin coating to form an insoluble phosphate layer at the interface between resin coating and galvanized steel. The electrochemical measurement clarified that the insoluble phosphate layer suppressed cathode reaction (reduction reaction of dissolved oxygen).
Crack growth kinetics across weld interface between Alloy 182 and LAS (Low Alloy Steel) and that between Alloy 182 and Metals to simulate weld dilution zone was investigated by CBB (Creviced Bent Beam) test. The main objective of this study is to investigate dynamic influence for a crack initiated in Alloy 182 to propagate into LAS. Specimens were subjected to CBB tests for 2000 h each in simulated BWR water with 8 ppm of dissolved oxygen. Mechanics conditions were described by equivalent stress intensity factor KJ values which are J values from elastoplastic analysis. In small-sized specimens of 2 mm in thickness, cracks which initiated in Alloy 182 propagated into Metal21-4 (20%Ni, 4%Cr), while they did not into Metal21-5 (10%Ni, 2%Cr). In moderate-sized specimens of 10 mm in thickness, cracks did advance into Metals and LAS under KJ values more than 80 MPa･m1/2.