WCN Autumn 2010

Corrosion Rate as a fuction of % Ce, % La in % Al in 5% NaCI

% Ce % La % Al

Linear (% Al) Linear (% Ce) Linear (% La)

Concentration Al ( %)

Concentration Ce & La (both in %)

Corrosion Rate (µm loss per year)

Figure 24 ▲ ▲ : Effect of mischmetal additions on corrosion rate in electrochemical potential test in 0.05M aqueous K2SO4 (8)

References

As temperature increased, faster alloy layer growth, and consequently wrapping test failures after shorter exposure times were observed to occur for both steel types having zinc coatings, but not zinc-5% aluminium coatings. Zinc-5% aluminium coatings have shown temperature resistance for periods at above 300°. Exact resistance times for zinc coated wires at elevated temperatures may likely be dependent on wire composition. At temperatures over 200°C, corrosion resistance of zinc-5% aluminium coated wires may actually improve slightly. Cerium and lanthanum mischmetal, required for the Galfan ® specification, do not have a significant impact in a well regulated Zn5Al coating operation. As much as half of such additions to the hot dip bath are wasted in the form of dross. The mischmetal that does remain in the coating was observed not to have significant impact on many aspects of corrosion resistance. This paper was given at the Istanbul Cable & Wire ‘09 conference, 2 nd November 2009. The authors were presented with the Harry W Bennett Ferrous speaker award at wire Düsseldorf 2010.

(1) “High Temperature Applications,” Dear Dr Galv, American Galvanizer, Vol 47, 2000 (2) H W Adams, “Steel Supported Aluminum Conductors (SSAC) for Overhead Trans- mission Lines,” Paper T 74 054-3, IEEE PES Winter Meeting, 1973 (3) S F Radtke, D Coutsouradis and J Pelerin, US Patent 4448748, “Zinc-Aluminum Alloys and Coatings,” 1984 (4) ASTM A856: “Specification for Zinc-5% Aluminum-Mischmetal Alloy-Coated Carbon Sheet,” American Society for Testing and Materials (5) H Dewilde, “Galfan: A Breakthrough in the Corrosion Protection of Wire Products,” International Technical Conference on Wire Technology, S ã o Paulo, Brazil, 1996, pp 97-105 (6) “Zinc-aluminum coating: management of Galfan ® lines,” R Branders and A Stacey, Wire Journal International, Nov 2008 (7) K Manchiraju, “Examination of Galvanized VS Bezinal Coated Steel Samples,” MP2003020, Southwire, 2004 (8) C Blakeman, G Lagae, J Karasek, Bekaert Internal Report, 2003

Charles Coffin, Hans Depamelaere, Dale King and Walther Van Raemdonck, NV Bekaert SA, Belgium Email: info@bekaert.com Website: www.bekaert.com

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