Corrosion Mechanisms of Steel and Cast Iron by Molten Aluminum
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IN the aluminum industry, a wide range of metallic components are immersed in liquid aluminum baths at temperatures higher than 963 K (690 °C). These structural components corrode in the liquid metal and are changed frequently because of the extensive corrosion, leading to a waste of time and money. In the literature,[1–3] the primary corrosion mechanism of Fe-based components in liquid Al is dissolution corrosion. New materials with improved corrosion resistance can be designed to build a structural part; however, a compromise between the corrosion resistance and the cost of the material has to be achieved. The production cost of cast iron is low. The properties of various cast iron grades can be optimized for specific applications such as mechanical stability,[4] aqua corrosion resistance,[5,6] ductility, absorption of vibrations, or resistance to the corrosion by liquid aluminum. The corrosion of cast iron by liquid aluminum has not been investigated expansively in the literature.[1–3,7,8] Most cast irons studied in this environment are grades for hot atmospheric corrosion with high contents in chromium, molybdenum, or silicon. Bastien and Daeschner[1] have studied the behavior of different grades of cast irons used for ingot molds. It DAVID BALLOY and JEAN-CHARLES TISSIER, Maıˆ tre de Confe´rences, are with the Univ Lille Nord de France, F-59650 Villeneuve d’Ascq, France. Contact e-mail: [email protected] MARIE-LAURENCE GIORGI, Maıˆ tre de Confe´rences, is with the Laboratoire de Ge´nie des Proce´de´s et des Mate´riaux, E´cole Centrale Paris, F-92295 Paris, France. MARC BRIANT, Inge´nieur Chercheur, is with the Commissariat a l’Energie Atomique, F-91191 Gif-surYvette, France. Manuscript submitted October 14, 2009. Article published online May 26, 2010 2366—VOLUME 41A, SEPTEMBER 2010
then is shown that a pearlitic matrix has a better corrosion resistance than a ferritic matrix and that additions of Mo or Cr do not improve the corrosion resistance. Podrzucki and Kosowski[2] have shown that the corrosion rate of cast irons in a liquid aluminum alloy containing 12 wt pct Si reaches a maximum when the Cr content is equal to 2.9 wt pct. These authors also have studied the influence of aluminum and have proposed, without any explanation, to add 4 to 5 wt pct Al to improve the corrosion resistance of cast irons. More recently, Galkin et al.[3] studied the corrosion of cast irons enriched with chromium (2.65 to 4.25 wt pct) and aluminum (2.53 to 6.46 wt pct). In all cases, the corrosion rate was lower for the unalloyed cast iron (–20 wt pct), and the variation of this corrosion rate with the amount of alloying elements was not significant (±2 wt pct). Gatto and Hugony[7] published a study on the corrosion of steels and Cr-Al-added cast irons in pure liquid aluminum. They showed that the loss in weight after 24 hours reaction in liquid aluminum was seven times more important for steel than for cast irons, but they did not find any beneficial effect of an addition of Cr or Al. The different behaviors observed with stee
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