Characterization of the Ag43Cu37Zn20 alloy surface after potentiostatic polarization using LDI-TOF mass spectrometry

This work is the first to demonstrate the possibilities of direct analysis of the corrosion film formed on Ag43Cu37Zn20 alloy using laser desorption/ionization (LDI) on a commercial matrix-assisted LDI time of flight mass spectrometry (MS) instrument. In the LDI mass spectra measured from the water solution of the corrosion film, the ion species Zn+, Zn(H2O)(+), AgH+, Cu2H+, Cu2O(OH)+, Cu3O(OH)(+) (high intensity), and Cu(OH)(H2O)(+), ZnCl(OH)(H2O)(+), AgCl+, CuCl+ (low intensity) were identified. The LDI mass spectra of the propan-2-ol solution of the corrosion film contains the ions Zn5Cl(OH)(3)(H2O)(11)(+), Zn5Cl2 (OH)(8) (H2O)(6)(+), and Zn5Cl2 (OH)(H2O)(14)(+). Mass spectra were observed at laser energies in the range of 1340-1860 arbitrary units in positive ion mode. Previously, Raman spectra and X-ray diffraction (XRD) analysis of the same anodic film have shown similar results as LDI MS -that the anodic film contains the mixture of Ag, Cu2O, CuCl, Zn5Cl2(OH)(8) center dot H2O, and beta-Zn(OH) Cl. LDI MS could be a complementary method for XRD and Raman, as demonstrated in this investigation. The LDI MS method greatly reduces the analysis time and amount of the sample compared to traditional methods. For this reason, the LDI MS method can be a useful tool for the fast qualitative screening of corrosion films.