純金属のV₂0₅融液による腐食生成物

抄録

Corrosion products of iron, cobalt, nickel, zirconium, chromium, and titanium in V₂0₅ melt were examined by metallography, electron probe microanalysis, and X-ray diffraction. The main results obtained are as follows:
(1) Iron. FeVO₄ and FeV₂0₆ in addition to wustite, magnetite, and hematite, were found in the corrosion products at 850°C. FeVO₄ and FeV₂0₆ were detected in the places which were melt at the test temperature. Magnetite layer formed at 850°C contained vanadium and its composition was considered to be (Fe₁-_xV_x) ₃O₄, while magnetite layer at 750°C did not contain vanadium.
(2) Cobalt. A porous and thick scale layer formed at 850°C mainly consisted of Co₃V₂O₈, and a considerably large amount of cobalt was observed in V₂0₅ melt.
(3) Nickel. A dense scale layer formed at 900°C mainly consisted of Ni₃V₂O₈, and only a small amount of nickel was detected in V₂O₅ melt. Low oxidation rate of nickel is considered to be due to the formation of the dense Ni₃V₂O₈ layer.
(4) Zirconium. ZrO₂ was formed at 850°C, and the scale was so porous that V₂O₅ melt penetrated into the innner part. The formation of ZrV₂O₇ besides ZrO₂ was observed at 700°C.
(5) Chromium. Solid CrVO₄ was observed in the scale in addition to Cr₂O₃ at 850°C. The former is considered to contribute to the good corrosion resistance of chromium.
(6) Titanium. The formation of TiO₂ (rutile) was observed.