questions

| November 16, 2015
  1. Please solve problems

 

  1. Please include images of: composition cells, stress cells, concentration cells, coatings, inhibitors, sacrificial anodes, impressed voltages, anodic protection, cold worked grain structure and recrystallized grain structure.

Question 2

SOLVING PROBLEMS

23-24

The leaf springs for an automobile are formed from a high-carbon steel. For best corrosion resistance, should the springs be formed by hot working or cold working? Explain. Would corrosion still occur even if you use the most desirable forming process? Explain.

Solution

23-25

Several types of metallic coatings are used to protect steel, including zinc, lead, tin, aluminum, and nickel. In which of these cases will the coating provide protection even when the coating is locally disrupted? Explain.

Solution

23-26

An austenitic stainless steel corrodes in all of the heat-affected zone (HAZ) surrounding the fusion zone of a weld. Explain why corrosion occurs and discuss the type of welding process or procedure that might have been used. What might you do to prevent corrosion in this region?

Solution

23-27

A steel nut is securely tightened onto a bolt in an industrial environment. After several months, the nut is found to contain numerous cracks. Explain why cracking might have occurred.

Solution

23-28

The shaft for a propeller on a ship is carefully designed so that the applied stresses are well below the endurance limit for the material. Yet after several months, the shaft cracks and fails. Offer an explanation for why failure might have occurred.

Solution

23-29

An aircraft wing composed of carbon fiber-reinforced epoxy is connected to titanium forging on the fuselage. Will the anode for a corrosion cell be the carbon fiber, the titanium, or the epoxy? Which will most likely be the cathode? Explain.

Solution

23-30

The inside surface of a cast iron pipe is covered with tar, which provides a protective coating. Acetone in a chemical laboratory coating. Acetone in a chemical laboratory is drained through the pipe on a regular basis. Explain why, after several weeks, the pipe begins to corrode.

Solution

23-31

A cold-worked copper tube is soldered, using a lead-tin alloy, into a steel connector. What types of electrochemical cells might develop due to this connection? Which is the materials would you expect to serve as the anode and suffer the most extensive damage due to corrosion? Explain.

Solution

23-32

Pure tin is used to provide a solder connection for copper in many electrical uses. Which metal will most likely act as the anode?

Solution

23-33

Sheets of annealed nickel, cold-worked nickel, and recrystallized nickel are placed into an electrolyte. Which is the most likely to corrode? Which is the least likely to corrode? Explain.

Solution

23-34

A pipeline carrying liquid fertilizer crosses a small creek. A large tree washes down the creek and is wedged against the steel pipe. After some time, a hole is produced in the pipe at the point where the tree touches the pipe, with the diameter of the hole larger on the outside of the pipe than on the inside of the pipe. The pipe then leaks fertilizer into the creek. Offer an explanation for why the pipe corroded.

Solution

23-35

Two sheets of a 1040 steel are joined together with an aluminum rivet. Discuss the possible corrosion cells that might be created as a result of this joining process. Recommend a joining process that might minimize corrosion for these cells.

Solution

23-36

Cross-section through an epoxy-encapsulated integrated circuit, including a microgap between the copper lead frame and the epoxy polymer. Suppose chloride ions from the manufacturing process penetrate the package. What types of corrosion cells might develop? What portions of the integrated circuit are most likely to corrode?

Solution

 

 

 

 

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