镍基固溶体增韧Cr_(13)Ni_5Si_2合金在含Cl~-溶液中的腐蚀行为

采用极化曲线,Tafel阿和电化学限抗谱(EIS)技术,研究了镍基固溶体增韧Cr_(13)Ni_5Si_2金属硅化物合金在不同Cl~-浓度Na_2SO_4+NaCl溶液中的电化学腐蚀行为,并对其表面钝化膜进行了X射线光电子能谱(XPS)分析.结果表明:由于超高的Cr含量易于在表面形成以Cr_2O_3为主的稳定钝化膜以及组成相Cr_(13)Ni_5Si_2和Cr3Ni5Si2高的化学稳定性,合金在不同Cl~-浓度溶液中均具有良好的耐蚀性;合金的开路电位,破裂电位和腐蚀电流密度等几乎不随Cl~-浓度的增加而改变,即合金对Cl~-浓度不敏感,在中性含Cl~-介质中耐蚀性优异.

CORROSION BEHAVIORS OF Ni BASE SOLID SOLUTION-TOUGHENED Cr_(13)Ni_5Si_2 ALLOY IN Cl-CONTAINING SOLUTIONS

From the application point of view, corrosion resistance of materials in corrosive environments, especially in Cl~- containing medium, has great significance when used as mechanical components serving in marine and other aggressive environments. The corrosion behavior of a material is largely controlled by the presence or absence of protective surface film, which may act as a protective barrier against corrosion attacks. Therefore, the corrosion resistance of an alloy is closely related to the particular composition of the passive film and the synergistic interaction between the cations of alloy components in the passive film. In the present study, a γ-toughened Cr_(13)Ni_5Si_2 metal silicide alloy, consisting of Cr_(13)Ni_5Si_2, Ni base solid solution γ and Cr_(13)Ni_5Si_2 was designed and fabricated by the introduction melting and die casting prosess. Corrosion behaviors of the alloy in a series of Na_2SO_4+NaCl solutions were investigated by anodic polarization, Tafel plot and electrochemical impedance spectroscopy (EIS) experiments. Chemical composition of the passive fihn and the surface of polarized samples were examined by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. A conunercial solution treated singlc phase austenitic stainless steel 1Cr18Ni9Ti was selected as the reference material for all the electrochemical tests. Results showed that the metal silicide alloy exhibited high corrosion resistance in all testing solutions due to the formation of a compact and protective passive film composed mainly of Cr_2O_3, as well as the high chemical stability of Cr_(13)Ni_5Si_2 and Cr_(13)Ni_5Si_2 phases. No evidence of localized corrosion occurred even after anodic polarization in 0.1 mol/L Na_2SO_4+1 mol/L NaCl solution. Moreover, the corrosion potential, breakdown potential and anodic current density are almost invariant with increasing Cl~- concentration, which means the alloy has excellent corrosion resistance in neutral Cl~- containing solutions.