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jenniz

新虫 (初入文坛)

应助: 0 (幼儿园)
金币: 4225
散金: 18
帖子: 35
在线: 42.1小时
虫号: 2515656
注册: 2013-06-20
性别: GG
专业: 有机分子功能材料化学

[求助] 【悬赏】求解几道题，在线急等！！谢谢！！

关于金属腐蚀方面的题目，请高手帮忙解答，可以用中文作答，谢谢！！
1. Which is better, a steel bolt in a brass structure, or a brass bolt in a steel structure? Why?

2.Using the Pourbaix diagram for nickel, give the anodic and cathodic reactions on Ni in water for the following conditions, assuming activity of 10-6 for all soluble species: (a) deaerated pH 2, (b) deaerated pH 10, (c) aerated pH 2, aerated pH 10.

3. A zinc specimen exposed to an acid solution loses 25 milligrams during a 12 hour exposure. If the specimen area is 200 cm2, (a) What is the equivalent current density flowing due to corrosion? (b) What is the corrosion rate in mm/year? (The density of zinc is 7.14g/cm3)

4. An electrochemical cell consists of cadmium immersed in a solution of CdSO4 and iron immersed in a solution of FeSO4. What concentration ratio [Cd2+]/[Fe2+] is required at 25℃ to prevent corrosion in the short-circuited cell? (φo (Fe2+/Fe) = -0.447 V, φo (Cd2+/Cd) = -0.403 V)

5. Consider that Cu2+ deposits as Cu in 0.2 M CuSO4 solution (activity coefficient = 0.15) at 25℃ and 1 atm at a potential of 0.19 V. Determine the current density taking the exchange current density, io, to be 10-9 A/cm2 and the Tafel constant, β, to be −0.05 V. (φo(Cu2+/Cu) = 0.342 V)

6.Palladium (like gold and platinum) is a noble metal. However, the Pourbaix diagram for palladium contains a region where palladium is subject to corrosion. Can palladium corrode by the following reaction: Pd(s) + 2H+(aq) → Pd2+(aq) + H2(g) ? Explain your answer.

7. According to the polarization curves in the following figure:
（1） For the anodic polarization curve, please specify the four regions according to different potentials and describe the state characteristic when the metal is in these four regions.
（2） What are the conditions for self-passivation of metals? According to polarization curves in the figure, the metal is not self-passivation. What methods can be used to realize self-paasivation of the metal in the figure?（15 points）

8. In what ways are crevice corrosion and pitting corrosion similar? In what ways are they different?

9. A steel tank car is used to transport a fertilizer solution. This solution is corrosive to steel, so it is necessary to provide some form of protection to the internal surfaces of the tank car. The tank car is equipped with a device which can control the electrode potential of the internal steel surface when the tank car is filled. The polarization curve for steel in the fertilizer solution is shown below.
(a) What is the corrosion current density of the steel in the freely corroding condition?
(b) What potential can be safely used in providing anodic protection?
(c) What is the corrosion current density at this applied anodic potential?
(d) Under the condition in Part (c), what is the loss of thickness of the tank car wall after a 10-day service period? Assume that the corrosion reaction is Fe → Fe2+ + 2e−. The atomic weight of Fe is 55.85 and its density is 7.87 g/cm3.
(e) What potential can be used if cathodic protection is applied to give the same corrosion rate as in Part (c)?

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