For each form of corrosion other than uniform, do the following: (a) Describe why, where, and the conditions under which the corrosion occurs. (b) Cite three measures that may be taken to nrevent or control it

Question: Describe the causes of pitting corrosion, crevice corrosion, galvanic corrosion, and intergranular corrosion and provide three measures to prevent or control each type. Answer: Pitting corrosion is caused by aggressive environments such as chloride-containing solutions and occurs in areas with a break in the protective oxide layer. Three measures to prevent or control pitting corrosion include selecting a material with a higher resistance to pitting, applying a protective coating, and regularly inspecting and cleaning the material. Crevice corrosion is caused by stagnant solutions or spaces where the environment is restricted, usually occurring in metal joints or gaps with low oxygen concentration. Measures to prevent or control crevice corrosion include designing structures to eliminate small gaps, using less susceptible materials or protective coatings, and regularly maintaining and cleaning the structures to avoid sediment accumulation. Galvanic corrosion occurs when two different metals or alloys are in direct contact with each other in the presence of an electrolyte, causing one of the metals to corrode faster due to their potential difference. Measures to prevent or control galvanic corrosion include isolating different metals with nonconductive materials, applying a protective coating or surface treatment to the anodic metal, and using a sacrificial anode. Intergranular corrosion results from selective attack on the grain boundaries of a metal or alloy, often due to differences in composition or exposure to a corrosive environment. Measures to prevent or control intergranular corrosion include using a low carbon variant of the material or alloy, performing a solution heat treatment to dissolve chromium carbides, and using a stabilization technique by adding stabilizing elements to the alloy.