During porcelainization the non-preoxidized alloy develops a Be-rich reaction zone in the interface which separates a Be-depleted alloy from a Li and (to a lesser extent Na) depleted region of the ceramic. Thus, Be diffuses to the interface through the alloy Be° → Be++ + 2 e- occurs at the interface; some of the electrons are electronically conducted to the porcelain-air interface where they are consumed as 2 e-+ ½ Oo2 → O=, and the resulting negatively charged porcelain surface attracts Li+ (and Na+).
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