Anna University Chennai 2003 B.Tech Metallurgy and Material Technology CORROSION AND SURFACE ENGINEERING - Question Paper

Time : 3 hours Maximum : 100 marks
ans ALL ques..

PART A — (10x2 = 20 marks)

1.Compare EMF series with galvanic series.
2.What is the importance of Pilling–Bedworth Ratio?
3.What are concentration cells?
4.What are oxygen scavengers? elaborate their applications?
5.How are corrosion testing methods divided? elaborate the advantages of pilot plant test?
6.What are the info expected from a good corrosion rate expression? Write the formula for the computation of corrosion rate in mpy units and identify the terms involved.
7.Define the term ‘exchange current density’. What is the influence of various metals on H2/H+ exchange current densities?
8.Draw a schematic combined polarization curve for a corrosion reaction of a metal and discuss the regions.
9.Write the principle involved in the electroless plating of Nickel. provide the composition of the bath used.
10.What are the industrial applications of anodizing of aluminium?

PART B — (5x16 = 80 marks)

11. Write a detailed account on boiler corrosion and boiler water treatment for corrosion control. (16)
12. (a)(i)Construct the Pourbaix diagram for iron–water system and
interpret. Bring out its advantage and limitations. (8)
(ii)How will you compute Langlier Saturation Index? Bring out its
significance. (8)
Or
(b)(i)Discuss the autocatalytic mechanism of pitting corrosion. Mention
the means of combating pitting corrosion. (8)
(ii)Write a brief note on the mechanisms of Stress Corrosion Cracking.
(8)
13. (a)Explain in detail the procedures to test the susceptibility of stainless steels to intergranular corrosion. (16)
Or
(b)Write an account on the testing of different specimens for susceptibility to Stress Corrosion Cracking. (16)
14. (a)Define all the 3 over potential terms. Derive the Tafel formula and interpret. (16)
Or
(b)Explain the electrochemical behaviour of an active passive metal. Write the criteria to be adopted in selecting an active passive metal for engineering application. (16)
15. (a)Write an account on the cathodic protection methods of corrosion control. Also discuss the mechanism of stray current corrosion. (16)
Or
(b)Discuss in detail the CVD coating method of nickel. elaborate the advantages and limitations of the CVD methods when compared to the PVD methods? (16)

Earning:   Approval pending.