Effects of Cr content on the corrosion behavior of porous Ni–Cr–Mo–Cu alloys in H3PO4 solution

Abstract

Porous Ni–Cr–Mo–Cu alloys were prepared via reaction synthesis of mixed powders. Electrochemical performance test and weight-loss method were used to evaluate the effects of chromium content in the range of 10 ∼ 30 wt% on the alloys corrosion performance in 30 wt% H _3 PO _4 solution. The microstructure, element valence and phase composition of the porous Ni–Cr–Mo–Cu alloys were characterized via scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and x-ray diffraction analysis (XRD), respectively. And the results show that the alloys exhibited serviceable corrosion performance and the corrosion behavior was better than that of pure Ni and Cu. Incremental changes in the chromium contents within a certain range enhanced the corrosion resistance of the alloys. These alloys with 30 wt% chromium exhibited excellent anti-corrosion ability in the H _3 PO _4 solution. The electrochemical test displayed that the double capacitive loops of the alloys in the H _3 PO _4 solution increased with the chromium content; at chromium content of 30 wt%, the charge transfer resistance and activation energy were 1123 Ω and 74.10 kJ mol ^−1 , respectively. The possible corrosion-inhibition mechanism was examined by XPS, which may be owing to the formation of MoO _x (x = 1, 2, 3) and Cr _2 O _3 passivation layers in the H _3 PO _4 solution, which prevent further corrosion in acid environments.

Keywords

• porous alloys
• Ni–Cr–Mo–Cu
• porosity
• passivation film