Inhibition of the hydrogen embrittlement of Ni-Ti superelastic alloy in an acidulated phosphate fluoride (APF) solution has been attempted by adding various amounts of H2O2. In a 0.2% APF solution, hydrogen absorption is markedly inhibited by adding H2O2, although corrosion is slightly enhanced by increasing the amount of added H 2O2. By adding a small amount of H2O 2 (0.001M), in the early stage of immersion, hydrogen embrittlement is inhibited and corrosion is only slightly enhanced. Upon adding H 2O2, it appears that the dominant cathodic reactions change from hydrogen evolution to H2O2 reduction reactions, or the surface conditions of the alloy are changed by H 2O2 with a high oxidation capability, thereby inhibiting hydrogen absorption. The present study clearly indicates that infinitesimal addition of H2O2 into acid fluoride solutions is effective for the inhibition of the hydrogen embrittlement of the alloy.
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