Technical articles

Nature of Adherence of Porcelain Enamels to Metals
by B. W. KING, H. P. TRIPP, and W. H. DUCKWORTH - Battelle Memorial Institute, Columbus, Ohio
TAn investigation of the fundamentals of the adherence of porcelain enamels to metals indicated that good adherence is the result of metal-to metal bonds between the atoms in the base metal and the proper metallic ions in the enamel.

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Adherence Mechanism Theory
Researchers throughout the time have suggested many theories of Enamel Adherence and it has seemed that the problem was solved, only to find new inconsistencies later on. Before discussing these theories, it is desirable to review some of the facts linked with the adherence phenomenon.
At some time during firing, the following statements are true

  1. Iron oxide is necessary at the iron-enamel interface
  2. Iron oxide dissolves in the enamel glass
  3. Water in solution in the glass reacts with the iron to form iron oxide and hydrogen
  4. Dendrites of iron, cobalt, nickel, and their alloys form at the interface
  5. Hydrogen from the reduction of the water dissolved in the glass enters the iron
  6. Molecular hydrogen trapped at the interface, either during or after firing, causes reboiling and fishscaling
  7. Ionic or atomic hydrogen passes easily through iron or glass, but molecular hydrogen will not pass through either, except when transferred as bubbles in the glass or riffs in the iron
  8. Hydrogen is present as ions, atoms, molecules, hydrides, or water
  9. Gases reported to be evolved during firing are hydrogen, carbon monoxide, carbon dioxide, carbon hydrides, nitrogen, and water
  10. Water is in solution in all glasses
  11. Since the glass is an electrolyte, when molten, plating can take place
  12. An oxidizing atmosphere is necessary in the early stages of firing

The study by B. W. KING, H. P. TRIPP, and W. H. DUCKWORTH - Battelle Memorial Institute, Columbus, Ohio on the on Nature of Adherence of Porcelain Enamels to Metals published on the Journal Of The American Ceramic Society –Vol.42 No.11, 1959, is going throughout above points trying to develop a coherent adherence theory. The conclusion they reached were:

  1. The bond between enamels and metals can be chemical in nature.
  2. Good adherence requires that the enamel at the interface be saturated with an oxide of the base metal, and this oxide must be one, which when in solution in the enamel, will not be reduced by the metal.
  3. Good adherence of enamels to metals appears to be the result of metal-to-metal bonding between the atoms in the base metal and metallic ions in the enamel when certain chemical and thermodynamic requirements are met.
  4. The oxides commonly known as adherence promoters help to establish and maintain the conditions necessary for good adherence without contributing directly to the bond developed.

Posting this article on IEI’s website has been done not because we are blind believers of this theory but because we are convinced that it will help enamellers to better understand the background of enamel adherence to metallic supports.

The International Enamellers Institute (IEI) wishes to thanks the American Ceramic Society’s Journal of The American Ceramic Society and John Wiley & Sons, Inc. for the courtesy of being allowed to post the King et al. article on IEI’s website

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Project and Design of the Porcelain Enamelled Steel Composites
by Silvano Pagliuca - I.E.I. Secretary General
The knowledge of mechanical and thermal properties of enamelling grade steel and of porcelain (vitreous) Enamels and the Stress-Strain analysis of vitreous-steel composite are the pillars for a correct designing of enamelled parts. Robustness of enamelled product throughout its in-use life requires that the design of the enamelled parts are developed according to specific rules and links aiming at reducing the stress / strain in the composites. The presentation “Project and Design of the Porcelain Enamelled Steel Composites“ was prepared by Silvano Pagliuca, I.E.I. Secretary General as a lesson to Italian Enamellers on behalf of C.I.S.P. - Centro Italiano Smalti Porcellanati and for disseminating porcelain enamel technical information to Italian students of Milano and Faenza Universities.

On October,11, 2011 this lesson was given by Silvano Pagliuca, IEI Secretary General at the Enamel School of Anadolu University, Eskisehir -Turkey in occasion of International Ceramic, Glass, Porcelain Enamel, Glaze and Pigment Congress –SERES11, organized by Turkish Ceramic Association and the Anadolu University.

This presentation could be available in power point version for all I.E.I.’s Affiliates Enamellers Associations upon request, if interested to disseminate this kind of technical information among their members in occasion of their national Congresses and technical trainings. The I.E.I.’ Secretary General, Silvano Pagliuca could be available to give the lesson, as well.

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Corrosion of Enamel for Chemical Industry by Neutral Water Medium.
by R. Lorentz
Published in: Mitteilungen Des Vereins Deutscher Emailfachleute E.V.
Volume 34, Brochure 5, Pages 65-76, May 1986

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Surface Tension and Fusion Properties of Porcelain Enamels
by Charles Baldwin, Sid Feldman
Ferro Corporation

High-temperature viscosity of glasses is an important key to understanding the phenomena that occur when firing porcelain enamels.

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Stress and Strain in Enamel-Steel Composites: A Practical Viewpoint
by William D. Faust, Ferro Corporation, Cleveland, Ohio USA
Enamels applied to steel have characteristics similar to bi-metallic strips. The stresses that are induced during the firing have a very practical value and can be beneficial to the after fired strength of the enamelled article. Understanding the limitations of the strains and stresses in enamels will aid in controlling the movement of parts that are exposed to high temperatures such as ovens and range tops.

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Stress Reduction in Porcelain Steel Systems
by John J. Jozefowski and Anthony R. Mazzuca by Pemco Corporation
The question most often asked of porcelain enamel technical personnel is, "What can be done to reduce chipping, minimize crazing, lower warping, and eliminate spalling on enamelled parts processed in various segments of the industry?"

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