Mechanisms of progressive degradation in ion-exchanged boroaluminosilicate glass: A comparative study

• Native and ion-exchanged boroaluminosilicate glasses follow divergent degradation pathways. • Ion-exchanged surfaces form a porous hydrogel skin due to thermodynamic instability. • Residual compressive stress suppresses pitting and preserves optical transmission. • Standard optical stress meters fail to detect the mechanically compromised surface skin. While the environmental durability of chemically strengthened alkali-boroaluminosilicate glass is paramount for consumer electronics, the mechanistic coupling between residual ion-exchange stress profiles and surface weathering kinetics remains poorly defined. This study presents a comparative analysis of the degradation mechanisms in ion-exchanged Corning® Gorilla® Glass 3 (I-GG3) and its native precursor (N-GG3) subjected to accelerated weathering protocols. N-GG3 follows a gel densification model, characterized by spontaneous repolymerization and syneresis during dry cycles, processes catalyzed by the hydrolytic stability of the residual aluminosilicate network. The volumetric shrinkage associated with this densification, constrained by the underlying bulk substrate, generates localized tensile stress fields that drive stochastic pitting. Conversely, I-GG3 undergoes network depolymerization driven by the thermodynamic instability and high chemical potential of the potassium-enriched surface. Rapid alkali leaching triggers a localized alkaline attack that selectively depletes intermediate network formers (Al, Mg), inhibiting densification and yielding a porous hydrogel layer. Despite the formation of this hydrated layer, the residual compressive stress profile suppresses vertical crack propagation, promoting a uniform dissolution regime that preserves optical transmission and bulk damage tolerance.