Chapter 16- Corrosion

Chapter 16- Corrosion - Chapter 16 1 ISSUES TO ADDRESS •...

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Unformatted text preview: Chapter 16 - 1 ISSUES TO ADDRESS... • How does corrosion occur ? • Which metals are most likely to corrode? • What environmental parameters affect corrosion rate? • How do we prevent or control corrosion? CHAPTER 16: CORROSION AND DEGRADATION OF MATERIALS Chapter 16 - 2 • Corrosion :-- the destructive electrochemical attack of a material.-- Ex: Al Capone's ship, Sapona, off the coast of Bimini. • Cost:-- 4 to 5% of the Gross National Product (GNP)*-- in the U.S. this amounts to just over $400 billion/yr** * H.H. Uhlig and W.R. Revie, Corrosion and Corrosion Control: An Introduction to Corrosion Science and Engineering , 3rd ed., John Wiley and Sons, Inc., 1985. **Economic Report of the President (1998). Photos courtesy L.M. Maestas, Sandia National Labs. Used with permission. THE COST OF CORROSION Chapter 16 - 3 • Uniform Attack Oxidation & reduction reactions occur uniformly over surfaces. • Selective Leaching Preferred corrosion of one element/constituent [e.g., Zn from brass (Cu-Zn)]. • Stress corrosion Corrosion at crack tips when a tensile stress is present. • Galvanic Dissimilar metals are physically joined in the presence of an electrolyte. The more anodic metal corrodes. • Erosion-corrosion Combined chemical attack and mechanical wear (e.g., pipe elbows). FORMS OF CORROSION Forms of corrosion • Crevice Narrow and confined spaces. Fig. 16.15, Callister & Rethwisch 3e . (Fig. 16.15 is courtesy LaQue Center for Corrosion Technology, Inc.) Rivet holes • Intergranular Corrosion along grain boundaries, often where precip. particles form. Fig. 16.18, Callister & Rethwisch 3e . attacked zones g.b. prec. • Pitting Downward propagation of small pits and holes....
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This note was uploaded on 09/05/2011 for the course EMA 3010 taught by Professor Unknown during the Summer '08 term at University of Florida.

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Chapter 16- Corrosion - Chapter 16 1 ISSUES TO ADDRESS •...

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