a. Corrosion is defined as the destructive and unintentional attack of a metal; it is electrochemical and ordinarily begins at the surface. Metallic corrosion is sometimes classified into eight forms: uniform, galvanic, crevice, pitting, intergranular, selective leaching, erosion-corrosion, and stress corrosion. For the galvanic corrosion, explain: i. Mechanism of corrosion. ii. Using galvanic series table, suggest three metals or alloys that may be used to galvanically protect nickel in the active state. ii. Propose three methods to reduce the effect of galvanic corrosion. (8 marks) b. Hydrogen embrittlement is, in a strict sense, a type of failure rather than a form of corrosion; however, it is often produced by hydrogen that is generated from corrosion reactions. i. Mechanism of hydrogen attack to the metal. ii. Propose three methods to reduce the hydrogen embrittiement. i: List three (3) examples of metal that is not considered susceptible to hydrogen embritlement. (8 marks) c. A piece of corroded steel plate was found in a submerged ocean vessel. It was estimated that the original area of the plate was 60cm2 and that approximately 1.3kg had corroded away during the submersion. Assuming a corrosion penetration rate of 100mpy for this alloy in seawater, estimate the time of submersion in years. The density of steel is 8.08 g/cm3. (4 marks)