Efficacy of zinc salts to protect glass against atmospheric alteration. Part II: Possible passivation mechanisms

To investigate the origin of the protection effect of zinc salts against glass atmospheric alteration, the speciation of Zn2+ ions on glass according to the deposit protocol and the Zn2+ surface concentration, and its change over time, was investigated in the light of the respective performances of the treatments. In that respect, a combination of various characterization methods of the glass surface and near‐surface was used before and after aging experiments (temperature, relative humidity (RH) control) of the Zn‐treated glass. Different Zn‐species could be observed on the surface of the treated glass: chemisorbed species, physisorbed species and precipitated hydroxide phases, their respective distribution being highly dependent on the nature of the treatment and on the Zn2+ surface concentration. GI‐XAS (Zn K‐edge) and ToF‐SIMS experiments pointed out the conversion by thermal activation of these surface species into chemisorbed species inserted in the glass network in the near‐surface. The chemisorbed species appear to be the most effective ones for the glass protection, possibly by making the surface less soluble, less hydrophilic and even by acting as a diffusion barrier. Evidences of the insertion of Zn2+ surface species in the glass network in the near‐surface by thermal activation.