Inhibition effect of underpotential deposition of metallic cations on aqueous corrosion of metals

Abstract

Abstract:The experimental results reported so far for the inhibition effect of underpotential deposition (UPD) of metallic cations on aqueous corrosion of metals are criticized and discussed based on the prerequisite for UPD. The inhibition effect of Pb 2+ , Cd 2+ , Zn 2+ or Mn 2+ on hydrogen evolution or hydrogen absorption on Armco iron or various steels is classified into three potential regions: bulk deposition, UPD and adsorption of metallic cations without discharging. Moreover, the inhibition effect of Pb 2+ , Tl + or Sn 2+ on anodic dissolution of pure Fe, Ni or Ni-base alloys in acidic solutions is ascribed to the UPD of these metallic cations. Particularly, in situ X-ray absorption spectroscopy (XAS) for Pb-UPD on Ni has indicated that the electrodeposited Pb species on the Ni surface is metallic to form partly surface alloy and the metallic Pb blocks the active dissolution sites of Ni to inhibit the anodic dissolution. In contrast, in situ XAS for Sn-UPD on Ni has indicated that the electro-deposited Sn species is not only bonded with Ni atoms but also bonded with oxygen atoms and that the anodic dissolution of Ni is inhibited by the oxygenated Sn species on Ni.

Synthesis, structural and the corrosion inhibition of phosphate-based xPbO–yB2O3–zP2O5 glass for C35 steel in acidic media

“…As mentioned above and the results obtained from the polarization method, we can suggest the following explanation (Fig. 6) that at potentials E < E eq Pb 2+ /Pb , the electrodeposition of bulk lead phase on iron occurs, indicated by the limiting diffusion-controlled value for lead deposition [46], at potentials E eq Pb 2+ /Pb < E < E eq Pb 2+ /Pb + ΔE UPD , where ∆E UPD is the UPD potential window [44], the peak that appeared may be due to the effect of underpotential deposition (UPD) of Pb 2+ , then at potentials E Pb 2+ ∕Pb + ΔE UPD < E , the decreases in cathodic and anodic currents are mainly due to the adsorption of Pb 2+ .…”

“…The results showed that the coverage of Me-adsorbate on the metal surface by the underpotential deposition of Me Z+ is the main mechanism that diminishes the effect of an aggressive environment. Masahiro Seo [44] also reported experimental results of the inhibition effect of bulk deposition, UPD, and adsorption of metal cations on the corrosion of different metals. Generally, in our case, as demonstrated in the polarization and EIS methods, a remarkable increase in charge transfer resistance is probably due to the mechanisms of bulk deposition, UPD and adsorption of lead ions, which decrease the cathodic and anodic current densities by inhibition of charge transfer hydrogen evolution and active iron dissolution process, respectively.…”

“…Moreover, Masahiro Seo had mentioned in his review article [44] that the inhibiting effect of metal cations on the corrosion of metals is possibly due to the effect of the underpotential deposition (UPD) of metal cations and also reported that the inhibition effect of some of the metal cations in cathodic polarization on steels is categorized into three potential zones: bulk deposition, UPD and adsorption of metal cations without discharging. In addition, the participation of UPD in corrosion only occurs if the work functions of substrate metal (Φ Fe = 4.5 eV) are greater than the work functions of electrodeposited metal (Φ Pb = 4.25 eV) [44]. Furthermore, the equilibrium potential of lead ( E eq Pb 2+ /Pb ) depends on the activity of Pb 2+ [45], as expressed in the following equation:…”

Inhibition of Anodic Dissolution of Steel by Sn2+ in Perchloric Acid Solution

“…Using cyclic voltammetry and in situ X-ray absorption spectroscopy (XAS), they observed that the anodic dissolution of the Ni substrate was concealed by the Pb-UPD 18,19 and Sn-UPD, 20,21 while the dissolution of the Fe and Fe-Ni alloy substrates was suppressed by Pb-UPD. 22 Subsequently, Seo discussed the possibility of Sn-UPD on iron and steels in a review article, 23 citing studies that reported the inhibition effect of Sn 2+ on the corrosion of iron and steels. Abdel-Aal et al suggested that the cathodic reaction on iron and carbon steel was inhibited by the UPD of Sn adatoms in carboxylic acid solutions; 17 however, no studies have discussed the suppression mechanism of Sn 2+ on the anodic dissolution of iron and steels from the viewpoint of UPD.…”