Inhibition of hydrogen embrittlement of Ni-Ti superelastic alloy in acid fluoride solution by hydrogen peroxide addition

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.