E45 - Lab 6 -Corrosion

E45 - Lab 6 -Corrosion - Engineering 45 Properties of...

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E E n n g g i i n n e e e e r r i i n n g g 4 4 5 5 P P r r o o p p e e r r t t i i e e s s o o f f M M a a t t e e r r i i a a l l s s L L a a b b o o r r a a t t o o r r y y © Copyright 2001 Professor Ronald Gronsky the Arthur C. and Phyllis G. Oppenheimer Chair in Advanced Materials Analysis University of California Berkeley, California 94720-1760
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E 45 2 Lab 6 Corrosion of Metals and Alloys Objectives To understand the electrochemical nature of aqueous corrosion To explore electrochemical methods of corrosion control Overview Corrosion is a complex phenomenon that incorporates elements of materials science, chemical engineering, chemistry, physics and quantum mechanics. This introduction is a brief qualitative exposure to some fundamental aspects of corrosion. Experiments are conducted to illustrate the galvanic series, electrode polarization, the oxygen concentration cell, galvanic current, and galvanic protection. Equipment weight percent sodium chloride solution (35 grams per liter of water) Strips of copper, brass, zinc, iron, mild steel, aluminum, nickel, and other metals. Calomel™ reference electrode 600ml beakers and electrode holders A ruler for measuring electrode areas Steel wool and sandpaper to clean the electrodes Clip leads to connect the various electrodes Corrosion Lab and Corrosion Lab Stripchart virtual instruments Mild steel sheet Phenolphthalein-ferricyanide indicator (20 grams sodium chloride, 2 grams potassium ferricyanide, and 2 ml phenolphthalein solution in 1 liter of water). Petri dish 100 Resistor Background Corrosion is an electrochemical process by which metallic species are caused to oxidize. The type of corrosion explored in this lab is aqueous (water) based corrosion, however corrosion can take place in solid electrolytes such as lithium polymer batteries, or in thin surface films, as in fuel cells. The most visible form of corrosion is the formation of oxides and hydroxides of iron, which we generically call “rust.” When we immerse mild steel into water, we observe the formation of rust. What we do not easily see is the reduction of oxygen that accompanies this process. If it were not for the reduction reaction, corrosion could not take place. Since corrosion is an electrochemical process, the release of electrons must be compensated by the consumption of electrons elsewhere (or else charge neutrality would be violated).
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E 45 3 Anodic reaction The reaction occurring at the anode in an electrochemical cell is an oxidation reaction in which a chemical species loses an electron. For example, an iron atom may loose two electrons forming a ferrous ion. Fe
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E45 - Lab 6 -Corrosion - Engineering 45 Properties of...

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