高張力鋼の過防食下における腐食疲労き裂進展(<小特集>腐食防食小特集)

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The influence of cathodic overprotection at E=-1.2V vs. SCE (Saturated Calomel Electrode) on the corrosion fatigue crack growth behavior of a high-tensil steel HT80 has been investigated at R=0.1-0.8 and f=0.1-0.01 Hz in 3.5% NaCl solution. The major acceleration factors dominating corrosion fatigue crack growth behavior under cathodic overprotection have been discussed. At the free corrosion potential (E=E_c), and acidified solution within cracks (pH=2) made the crack wall dissolve and the crack blunting, which causes a decrease in K_<op> from that in dry air. At E=-1.2V vs. SCE the pH value within cracks was 10, causing an increase in K_<op> due to the caustic corrosion products(caustic corrosion-products induced wedge-effect). The effect of load ratio on da/dN at E=E_c was negligible in terms of ΔK_<eff>. At E=-1.2V vs. SCE da/dN at R=0.8 accelerated from those at R<0.8 at high ΔK_<eff>, which was brought about by static SCC being dominating crack growth behavior. On the other hand, da/dN became greater as the frequency decreased both at E=E_c and E=-1.2 V vs. SCE. The major acceleration factor was hydrogen embrittlement at E=E_e, whilst they were hydrogen embrittlement and stress-assisted caustic dissolution at low ΔK_<eff>, and hydrogen embrittlement at high ΔK_<eff> at E=-1.2 V vs. SCE.
社団法人日本材料学会の論文
1984-11-15