The effect of rare earth metals on the microstructure and electrochemical corrosion behavior of lead calcium grid alloys in sulfuric acid solution

The effect of the rare earth element lanthanum (La) on the microstructure of lead–calcium grid alloys was studied by the metallographic microscope. A comparison of the electrochemical corrosion behavior of the new and traditional grid alloys was investigated by cyclic voltammetry (CV), A.C. impedance and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to study the surface morphology of anodic films of Pb–Ca–Sn–Al–Re alloys formed in sulfuric acid solution at 1.3 and 0.9 V for 2 h. The morphology of the corrosion layer was analyzed by SEM after the constant current corrosion test. The results show that an appropriate content of La can effectively (1) increase the fineness of the grain of Pb–Ca–Sn–Al alloys, (2) increase the growth of PbO2 film, and (3) make the anodic film formed at 1.3 V become fine and compact. Alloys with contents of 0.01 wt.%, 0.03 wt.% and 0.1 wt.% La were shown satisfactory results. La also can decrease the growth of Pb(II) film, purify and increase the density of the anodic film at 0.9 V, especially for La content of 0.03 wt.% and 0.1 wt.%. Moreover, La can improve the corrosion resistance of Pb–Ca–Sn–Al alloys, particularly for a La content of 0.01 wt.%.

► We have prepared a novel Pb–Ca–Sn–Al–La alloy, the fineness of the grain was increased by La.
► The La to Pb–Ca–Sn–Al alloy can increase the growth of PbO2, fine and compact anodic film at 1.3 V.
► The La can decrease the growth of Pb(II) at 0.9 V, clear and increase the density of the anodic film.
► La can increase the growth of dendritic crystals, improve the corrosion resistance of Pb–Ca–Sn–Al alloys.