電析非晶質Crおよび非晶質Cr2元合金の耐食性

抄録

This report describes the corrosion resistance of electrodeposited amorphous chromium and amorphous binary chromium alloys. The structure of electrodeposited chromium became crystalline or amorphous according to the condition of electrodeposition. Amorphous binary chromium alloys—Cr-W, Cr-Mo, and Cr-Fe—were obtained from the baths for amorphous chromium deposition in which W, Mo, or Fe ions were added. First, the corrosion resistance of amorphous chromium was compared with that of crystalline chromium to investigate the effect of the structure of electro-deposited chromium on the corrosion resistance. Then, the corrosion resistance of amorphous binary chromium alloys were compared with that of amorphous chromium to investigate the influence of alloying elements on the corrosion resistance. The corrosion resistance was examined by the electrochemical method. Anodic polarization curves were measured by the potentiodynamic method with the potential sweep rate of 2.0×10⁻³ V/s in 1 kmol/m³ HCl and 1 kmol/m³ H₂SO₄ in air at room temperature. The polarization curves showed that crystalline chromium was passivated only by anodic polarization, whereas amorphous chromium and binary chromium alloys were passivated spontaneously in the solutions. Accordingly, the corrosion resistance of electrodeposited chromium was improved remarkably by the structure change from a crystalline state to an amorphous state. Furthermore, the corrosion resistance of the amorphous binary chromium alloys was superior to that of amorphous chromium.