prbset114324 - for the two materials. For such conditions,...

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EMA 4324 Problem Set 11 11-1 [Jones 6-5] Equal 1-cm 2 areas of metals P and Q are immersed together in sulfuric acid of unit H+ activity having no other dissolved oxidizers. Using the electrochemical parameters listed below: [a] Determine corrosion potential and corrosion rate for each, when they are uncoupled; [b] When P and Q are electrically coupled, determine the potential and current passing in the galvanic couple so formed; [c] Determine the corrosion rates for P and Q when the two are galvanically coupled; [d] Which metal is cathodically protected upon galvanic coupling?; [e] On which metal is the hydrogen evolution rate increased upon galvanic coupling? 11-2 [Jones 6.6, modified] [a] By appropriate manipulation/adjustment in electrochemical parameters use polarization diagrams to show conditions in which the corrosion potential of a galvanic couple will not fall between the uncoupled Nernst potentials
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Unformatted text preview: for the two materials. For such conditions, which of the two metals is cathodically protected? Which of the two is galvanically corroded? Is it possible for two coupled metals to both be galvanically corroded? [b] Is it possible for the corrosion potential of two coupled metals to lie between the corrosion potentials for the two uncoupled metals? How or why not? 6-7. Plot the polarization curves and determine the galvanic corrosion rate [a] when 1-cm 2 of metal C is coupled to 1-cm 2 of metal A in a corrosive solution.; [b] when 10-cm 2 of C is coupled to 1-cm 2 of A in the same solution; [c] when a solution resistance of 3000 ohms is present between A and C in [b]. 0.1 10-5 2x10-6-0.6 Q 0.1 10-6 3x10-7-0.5 P b i o (C,H) i o (A) E eq material 10-6 0.1 0.04 C 10-7 0.1 0.05 A I corr , A b C , volts b A , volts material E corr (C) - E corr (A) = 0.500 v, with C noble to A...
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