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Metal Protection Crossion

DBT 303 METALS PROTECTION ASSIGNMENT 1 1) 2) 3) What is meant by oxidation and reduction processes? What is meant by anode and cathode? Write both half reaction equations and total equations in an electrochemical cell that consists of Pb and Zn in their respective 1M ion solutions. 4) Write both half reaction from the total equilibrium electrochemical cell below? Define what happen for each half reaction? Calculate the voltage that is generated Zn + 2HCL->ZnCl2 + H2 5) What is meant by Corrosion Penetration Rate, CPR? (i) (ii) Define CPR. Give its unit.

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) 7) 8) State three (3) corrosion medium? State the difference between EMF series and galvanic series that you know? What is meant by? (i) (ii) Corrosion? Corrosion rate? 9) One half of an electrochemical cell consists of a pure Nickel electrode in a solution of Ni2+. The other is a Cadmium electrode immersed in a Cd2+ solution. (i) If the cell is a standard one, write the spontaneous overall reaction and calculate the voltage that is generated. (ii) Compute the cell potential at 25? C if the Cd2+ and Ni2+ concentrations are 0. 5 and 10-3 M, respectively.

Is the spontaneous reaction direction still the same as for the standard cell? 10) 11) Define passivity. Give an example of passivity. Briefly explain how passivity behaviour protects the metal surface from further corrosion. 12) 13) 14) 15) State two (2) examples of metals that displays passivity behaviour. Define erosion corrosion and how does it happen? What is crevice corrosion? Give an example of crevice corrosion. Where are intergranular corrosion always occur? How to prevent intergranular corrosion? 16) A piece of corroded steel plate was found in submerged ocean vessel.

It was estimated that the original area of the plate was 15 in. 2 and approximately 2. 8 kg had corroded away during the submersion. Assuming a corrosion penetration rate of 180 mpy for this alloy in seawater, estimate the time of submersion in unit of years. The density of the steel is 7. 9 g/cm3. 17) 18) 19) 20) How does Activation Polarization occur? Explain about sacrificial anode and in what environment can be used? Explain about impressed current and how does it operated? Give four (4) common methods to apply metallic coating?