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مقاله 8، دوره 19، شماره 0 - شماره پیاپی 1000161، فروردین 1350 اصل مقاله (332.19 K) | ||
نویسنده | ||
الیده سرابی* | ||
عنوان مقاله [English] | ||
Passivity of Metals | ||
چکیده [English] | ||
Under mildly oxidizing conditions, some metals exhibit the property of passivity. Passivity is a state of electrochemical inactivity which is probably caused by a layer of metal oxide or adsorbed oxygen on the metal surface. Examples of metals displaying active-passive transitions are iron ,chromium ,nickel and titanium. In this paper the shape of the anodic polarization curve for an active passive metal is discussed, and the importance of the Flade potential and the critical passivating current density is illustrated. Since passivity provides metals with a natural corrosion resistance, methods for achieving passivity have been investigated. The following methods have been discussed: a- Alloying Iron with chromium, nickel and molybdenum to produce the stainless steels. b- Addition of passivators to liquids in contact with Iron. c- Noble-metal alloying for improving the corrosion resistance of titanium and chromium in deaerated acid solutions. In addition, the breakdown of passivity by chloride Ions has been briefly described. | ||
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