The effect of ZnAl-LDHs-CO3 on the corrosion behaviour of Zn-5Al alloys in 3.5wt.% NaCl solution

Role of Al and Mg alloying elements on corrosion behavior of zinc alloy‐coated steel substrates in 0.1 M NaCl solution

“…The twin peaks of Zn 2p 3/2 (1022.5 eV) and Zn 2p 1/2 (1044.5 eV) can be observed from the XPS survey spectrum of all the samples after immersion for 168 h, which was characteristic of Zn 2+ species. [ 15 ] Besides, the peaks of Zn LMMa (495.0 eV) and Zn LMMb Auger (474.0 eV), which confirmed corrosion products of oxidized Zn, were also observed in Figure 5. [ 22 ] The XPS spectra of C 1s (Figure 7) present the presence of the highest binding energy at about 290.5 eV, which was attributed to inorganic carbonate.…”

“…Besides, the characteristic peaks of ZnO were also detected in the corrosion products of the ZA sample during immersion time. [ 15,21 ] The buffering effect of Mg dissolution from the ZM surface resulted in the inhibition of the formation of ZnO [ 18 ] ; thus, their characteristic peaks cannot be observed in the XRD pattern (Figure 5c).…”

“…[ 22 ] The XPS spectra of C 1s (Figure 7) present the presence of the highest binding energy at about 290.5 eV, which was attributed to inorganic carbonate. [ 15 ] The other carbon‐containing functional groups such as C–C and organic C–O, which were commonly attributed to surface contamination during exposure to air, were also seen from the C 1s XPS peak. [ 23 ] The peak of Cl 2p (199.0 eV) was observed from the XPS survey spectra of the HDG substrate (Figure 6a), confirming the formation of simonkolleite on the HDG surface.…”

“…Therefore, due to anodic reactions, only Zn 2+ cations were formed (Equation ) in the cases of HDG and ZA, in contrast, both Mg 2+ and Zn 2+ cations were provided (Equation ) during the ZM corrosion. [ 7,10,15 ] The cathodic reaction corresponded to the reduction of oxygen in the Al‐rich phase (Equation ) [ 15 ] $$$\text{Zn}\,\to \,{\text{Zn}}^{2+}+2{{\rm{e}}}^{-},$$$ $$${\text{Zn}}_{2}\text{Mg}\to 2{\text{Zn}}^{2+}+{\text{Mg}}^{2+}+6{{\rm{e}}}^{-},$$$ $$${{\rm{O}}}_{2}+4{{\rm{e}}}^{-}+2{{\rm{H}}}_{2}{\rm{O}}\to 4{\text{OH}}^{-}.$$$…”

“…Besides, the presence of the different Al and/or Mg contents had an obvious effect on the phase structure of ZnAl (ZA) and ZnAlMg (ZM) alloys, which resulted in the intrinsic reactivity of the Zn‐based coatings; thus, complex precipitated corrosion products can be formed. [ 15 ] The previous research attributed the enhanced corrosion protection of the ZA and ZM alloy coatings to the density of new corrosion products after immersion in environments containing chloride, which can impede oxygen diffusion. [ 3,16 ] They found that the formation of hydrotalcites (HTs) by coprecipitation of the corresponding ions, having the chemical formula of [M 1 − x 2+ M x 3+ (OH) 2 ][A n − ] x / n ·mH 2 O (where M 2+ and M 3+ present divalent and trivalent metallic cations, respectively, and the A n − presents interlayer anions), contributed mainly to the enhanced anticorrosion properties of the ZA and ZM alloys coatings.…”