7. (a) Briefly describe the phenomenon of passivity. Why are stainless steels more corrosion resistant in many environme

[answerhappygod]

7. (a) Briefly describe the phenomenon of passivity. Why are
stainless steels more corrosion resistant in many environments than
plain carbon steels? (6 marks) (b) Consider the crystal form of
MgO. (i) Calculate the fraction of ionic bonding of MgO. Given that
the electronegativity of Mg and O are 1.2 and 3.5, respectively.
(ii) If Mg atom in MgO is substituted with Na, what type of defect
will be produced and which atom must be removed from the crystal?
(iii) If O atom in MgO is substituted with Cl, what type of defect
will be produced and which atom must be removed from the crystal?
(8 marks) (c) Briefly describe the following in relation to the
corrosion of materials: (i) Cathodic protection (ii) Corrosion
inhibitor (6 marks)