The figure on the left shows a water pump. The pump experienced some damage on the inside wall surfaces. The figure on the right shows a close-up view of an area of the flange surface. The grey regions indicated by the arrows are the damaged surfaces facing the water. These damaged layers are found to be porous and have no strength. (a) Is this likely to be a sign of (i) galvanic corrosion, (ii) intergranular corrosion, or (iii) selective leaching corrosion? (b) Briefly explain the mechanism of this form of corrosion. (c) What is the likely type of cast iron that the pump is made of? (d) If pump is cast in a wrong type of cast iron, what would be the right type to avoid this corrosion damage