Microalloy Precipitation at the Glass–Steel Interface Enabling Adherence of Porcelain Enamel

Abstract

The adherence of vitreous enamels on steel plates is studied clarifying the mechanisms taking place at the interface during firing. Evidence is provided from electron microprobe analysis for an iron alloy precipitation at the interface, which results from oversaturation of ferrous iron in the enamel glass. Subsequent coalescence of the alloy particles is observed but only after their bonding to the base metal adherence after cupping is achieved. The formation of microalloys requires Co2+, Ni2+, and Cu2+ ions in the enamel glass. A selective dissolution of the base metal by the latter cations does not occur.

Exploring the hindering mechanism of element Ti on the adherence of CoO‐bearing one‐coat enamel/steel

“…This consumes part of Co 2+ ions in the FeTiO 3 ‐rich region. It is believed that the way of precipitation of Fe–Co alloys can be divided into two types: homogeneous nucleation and non‐uniform nucleation . It is easier for Fe–Co alloys to precipitate out by attaching to the surface of steel or to the Fe–Co precipitates (II) than by homogeneous nucleation.…”

Micro‐alloys precipitation in NiO‐ and CoO‐bearing enamel coatings and their effect on adherence of enamel/steel

“…However, for MTNi3 and MTCo3 coatings, it is worth noting that after the deposited enamel powders melt, Fe‐Co or Fe‐Ni micro‐alloys precipitate out in the enamel coating upon the surface of oxide layer …”

“…As the oxide layer rapidly dissolved into the enamel coating, Co 2+ ions or Ni 2+ ions in the enamel will react with Fe 2+ ions. It is assumed that the reactions follow:…”

“…Meanwhile, the steel surface provides nucleation sites for the alloy precipitation. Therefore, micro‐alloys grow up there and gradually connect to the outer alloy precipitations that have already formed during stage II, forming a so‐called “anchor point,” leading to a high degree of mechanical interlocking between glass and metal …”

“…Among all the metal oxides, CoO and NiO are the two best choices. Therefore, many studies have been conducted to investigate their roles in enhancing enamel‐steel interfacial adherence, and micro‐alloy precipitations at the interface between steel and enamels . These different micro‐alloy precipitations affect their adherence .…”