Corrosion Atmosférica

Instituto

Politécnico Nacional

Escuela Superior de Ingeniería Química e industrias extractivas

Departamento de Ingeniería en Metalurgia y Materiales

Corrosión

“Respuesta a las preguntas del primer capítulo”

Presenta: José Auristel Ovando Jiménez

Recibe: Dra. Elsa Arce

México, D.F. 24 de Agosto de 2012

1-1. Radial steel belted automobile tires are commonly constructed of rubber reinforced with braided steel wire, each strand coated with copper. The copper coating is included to enhance adhesion of the rubber tire casing to the wire.

How might corrosion contribute to tire failure? Which forms of corrosion might be involved?

1-2. What costs (Section 1.2) might be involved in tire failures in Problem 1-1 above?

1-3. In the steam return pipe failure described in Section 1.2.2, what are some of the costs which may result from this and similar failures?

1-4. For iron corroding in acidified, aerated seawater, write the probable anodic and cathodic reactions.

1-5. The corrosion rate of titanium was measured at 100 mpy in dilute sulfuric acid which was free of dissolved oxygen and other dissolved oxidizers. Iron was found to corrode at 250 mpy in the same conditions in separate tests. Contamination by Fe+3 ion produced a decrease in corrosion rate of titanium to 1.5 mpy and an increase in the corrosion rate of iron to 3500 mpy. Explain how this could be possible.

1-6. If polarization in Problem 1-5 were zero, what would be the corrosion rate in each case?

1-7. The material for the piping system must be specified to carry hot aerated seawater used to cool steam in a new power plan to Stresses both static and cyclic are present in the pipe due to welding, weight of the pipe, and vibrations from the pumps. Flow will vary from stagnant to very rapid. Austenitic stainless steel and 70Cu-30Zn brass are being considered for the pipe. What forms of corrosion might be possible for each material? Which alloy would be better?

1-8. (a) Derive the expression for corrosion rate in MPY given in Equation (9). (b) Show how the constant 534 in this equation changes to 87600 when units of corrosion rate change to micrometers per year with area measured in cm2.

1-9. A carbon steel test specimen of dimensions 2” x 3” x 0.125” with a 0025” hole for suspending in solution is exposed for 120 hours in an acid solution and loses 150 milligrams. Calculate the corrosion rate in mpy and mm/yr.

1-10. What experimental precautions must be taken to ensure maximum accuracy in the measured weight loss of Problem 1-9?

1-11. Three more identical test specimens are included with the one from Problem 1-9 in a planned interval testing program. One is exposed for 12 hours and loses 25 mg. A second is exposed for 108 hours and loses 130 mg. The third

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