Prediction of new additives for galvanizing process by the properties of their constituent chemical elements
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Prediction of new additives for galvanizing process by the properties of their constituent chemical elements HongMei Jin and Yi Li Department of Materials Science, National University of Singapore, Lower Kent Ridge Road, Singapore 119260
Ping Wua) Institute of High Performance Computing, 89B Science Park Drive, #01-05/08, Singapore 118261 (Received 1 May 1998; accepted 20 November 1998)
Chemical element properties are generally classified in six groups: size, atomic number, electrochemical factor, valence-electron, cohesive energy, and angular valence-orbital. It is well known that some bulk properties of materials, like electrical conductivity and heat capacity of metals, may be interpreted in principle based on their constituent chemical element properties. In this study, effects of additives in galvanizing have been correlated to the chemical element properties of the additives. By screening all chemical elements (in the periodic table of elements) with this model, new additives, like Ca, Sc, Ge, Sr, and Y, have been predicted to reduce the steel weight loss in galvanizing. This model may also help to design new alloys as additives.
I. INTRODUCTION
Traditionally, the crystal structure of a compound, which plays a key role in determining its bulk properties,1 is fully defined by the following data: (i) chemical formula, (ii) space group and unit-cell dimensions, and (iii) coordinates of the point sets (atomic positions) and their occupancy. In literature, over 4000 different structures classified by these data have been reported.2 Because of the large number of different structures, it is practically impossible to find connections within crystal structures, which makes it difficult to predict bulk properties of materials from their crystal structures. To reduce the number of distinctly different crystal structures, Villars and Daams2–4 applied the atomic-environment approach. They also proposed to correlate the redefined crystal structure (by atomic-environment approach) with the following six groups of its constituent chemical element properties: (i) size factor (Sf ), (ii) atomic-number factor (Af ), (iii) electrochemical factor (Elf ), (iv) valenceelectron factor (Vf ), (v) cohesive-energy factor (Cf ), and (vi) angular valence-orbital factor (Anf ). It is often difficult to design new additives for zinc galvanizing starting from first principles. In this study these factors of additive elements were used to correlate the bulk properties of additives, regardless of their effects on the crystal structures in the coatings. Hot dip galvanizing (in which the steel articles are dipped in the molten zinc-galvanizing bath) is one of a)
Address all correspondence to this author. J. Mater. Res., Vol. 14, No. 5, May 1999
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the principal technologies to protect against atmospheric corrosion of steel. The protective zinc coating on steel consists of three intermetallic zinc-iron layers: delta, zeta, and gamma phases.5
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