Comparison of the corrosion resistance behaviour for two metal-metal glassy alloys in neutral solution with chloride impact

Highlights: • Electrochemical behaviour of Fe-Co glassy alloys are investigated in neutral solution. • Adding Cl⁻ ion decreased alloys resistivity and displays localized attack. • High resistance of VX9 alloy related to the dielectric properties of a passive film. • The passive film on VX9 alloy include of p-type semiconductor (Cr₂O₃,MoO₂ and Al₂O₃₎. • VX50 alloy surface covered by salt scales. The electrochemical behaviour of bulk glassy Fe₇₈Co₉Cr₁₀Mo₂Al₁ and Fe₄₉Co₄₉V₂ alloys was investigated using electrochemical techniques with different concentrations of Na₂SO₄ solution (0.25, 0.5 and 1.0 M). The alloys surfaces were characterized by various morphology and composition techniques. The corrosion rate of the two alloys is inversely proportional to the concentration of Na₂SO₄ solution. The VX9 alloy exhibited spontaneous production of a good passive layer in Na₂SO₄ solutions as a response to the presence of protective elements, such as Cr (10%), Mo (2%) and Al (1%). No passivation occurred on the surface of the VX50 alloy, with only salt precipitating on it. Adding chloride reduces the resistivity of both alloys as it is a localized attack.