prbset05_key4324

# prbset05_key4324 - following parameters on the corrosion...

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EMA 4324 Problem Set 5 1. A zinc specimen exposed to an acid solution loses 25 milligrams during a 12 hour exposure. [a] What is the equivalent current flowing due to corrosion? [b] If the specimen area is 200 cm 2 , what is the corrosion rate in mils per year [mpy] due to this current? ****************************************************** 25 mg*g/1000mg = 0.025 g Zn*mol/65.38 g*2 eq/mol*96500/eq = 73.7 C /12hr*hr/3600 s = 1.71x10 -3 C/s = 1.71 mA 1.71x10 -3 A/200 cm 2 = 8.54x10 -6 A/cm 2 *eq/96500 C*mol/2 eq*65.38 g/mol*cm 3 /7.13 g = 4.06x10 -10 cm/s *in/2.54cm*1000 mil/in*3600 s/hr*24 hr/day * 365 day/year = 5.04 mpy .... 2. Using appropriate polarization diagrams, determine the effect of the
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Unformatted text preview: following parameters on the corrosion potential and corrosion rate of metal M corroding to M + in an acid solution: [a] increasing j o of the anodic reaction, [b] increasing j o of the cathodic reaction, [c] increasing the concentration of dissolved [H + ] and [d] increasing the Tafel constant for the anodic reaction. ****************************************************** decrease increase increase b (anodic) increase increase increase [H + ] increase increase increase j o (cathodic) increase decrease increase j o (anodic) I corr E corr parameter...
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