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The recent Corrosion Engineering publication by McGraw-Hill was designed as a textbook to accompany the education of undergraduates, graduates and other technical trainees during their discovery of the modern world of corrosion engineering. The book contains many equations and principles that lend themselves to the production of assignments and questions that are so important to evaluate newly acquired skills.
Note to Instructors: the following assignments listed here are to help you in preparing and delivering high quality courses on the subject. Your feedback and suggestions are an important part of the quality assurance and improvement process. Please do not hesitate to send your comments or questions to our
* The questions marked with an asterisk are used as example problems throughout the CCE 281 distance course material and their solutions are available online.
Chapter One: The Study of Corrosion(Visual aids)
Discuss the evolution of the knowledge of metallic corrosion over the past centuries
Elaborate on the roles of a corrosion engineer.
What are the main responsibilities of a corrosion engineer? ... of a corrosion scientist? ... of a corrosion technologist?
*Describe a corrosion problem encountered in your immediate surroundings and discuss its relative importance.
Explain the purpose and chemistry of a ferroxyl indicator.
Provide some examples of what has been revealed about corrosion processes by the use of a ferroxyl indicator.
Search the open literature for methods that have been proposed to visualize corrosion processes on various metals and alloys.
*Explain what are the main differences between direct and indirect costs associated to corrosion damage. Provide some examples from your own experience.
Chapter Two:Corrosion Basics (Visual aids)
Describe the main ore species associated with iron, copper, aluminum, and zinc.
Describe some of the components, present in most ores , that make ore processing so corrosive.
*Compare the energy required to produce one metric ton of magnesium from its oxide to the energy required to convert enough copper oxide to produce one ton of metallic copper.
*Discuss the energy values presented in Table 2.2 in relation to the order in which metals and associated alloys appeared in the history of mankind.
Compare the order in which metal oxides are arranged in Table 2.2 to the order in which the parent metals are organized in the electromotive series presented in Tables 4.1 and 4.2.
Compare the chemical arrangement in salts with the main crystal structures of the main metals used in engineering.
Discuss the unit cell concept to describe metals.
Describe a detailed procedure to reveal austenite boundaries in tempered steels; ... carbides in cold rolled and annealed steel; ... the general structure of stainless steels.
What is the ASTM grain size number of an alloy for which we count 16 grains per square centimetre in a photomicrograph taken at magnificationX100.
The yield strength of mild steel with an average grain diameter of 0.05 mm is 140 MPa. The yield strength of the same steel with a grain diameter of 0.007 mm is 280 MPa. Use Hall-Petch relation to estimate an average grain diameter for the same steel with a strength of 210 MPa.
Estimate the ASTM grain size number of the 70 Ni 30 Cu alloy shown in Figure 2.6b.
*A solution is made up to contain 0.01 M HCl. What is its pH?
*A solution is made up to contain 0.01 M NaOH. What is its pH?
*A solution contains a mixture of sodium bicarbonate (0.05 M) and sodium carbonate (0.2 M).What is its pH?
Would you add and acid or a base to increase the carbon dioxide (CO2) pressure in the solution described in the previous question? Explain your answer and relate this situation to the pH that exists in a pop (soda) bottle.
Many corrosion problems associated with oil & gas exploitation are attributed to hydrogen sulfide (H2S) and its derivatives. Knowing that the two pKa for this acid are respectively 7.04 and 11.96, describe what would be the dominant sulfide species for a solution with a known pH of 6.0. What would be the relative fraction of dissociated sulfide ions present at this pH?
24 g of zinc are dissolved in 1 M HCl solution. How many moles of hydrogen gas would be produced during this corrosion reaction? (see equation 2.10 and the periodic table in Appendix B)
24 g of iron are dissolved in 1 M HCl solution. How many moles of hydrogen gas would be produced during this corrosion reaction? (see equation 2.15 and the periodic table in Appendix B)
Provide an explanation for the patterns of oxidation states, in Figure 2.9, that are repeated between rows 4, 5 and 6 of the periodic table.
Describe some possible manganese oxidation products and propose an explanation for the large number of oxidation states supported by manganese.
Chapter Three: Corrosion Electrochemistry (Visual aids)
Describe the principles of a Daniell cell and elaborate on the usefulness of the Daniell cell when it was introduced.
*Why is a separator commonly used between the anodic and cathodic half cells of a Daniell cell?
*Elaborate on the effect the absence of a separator would have on the potential generated by a Daniell cell. Make reference to the Nernst equation described in Chapter 4 to support your arguments.
Why is the zinc electrode of a Daniell cell also called 'the negative' in battery parlance. Are there similarities between the anode material of a Daniell cell and anodes of some batteries or cells commonly used today?
*Write a short-hand description of the reactions involved in the corrosion of zinc as illustrated in Figure 3.3.
Write a short-hand description for the two sets of reactions involved in the corrosion of zinc as illustrated in Figure 3.6.
*Why are there always a minimum of two electrochemical reactions to explain even the simplest corrosion reaction?
What is an anodic process in a corrosion reaction? Provide some examples.
What is a cathodic process in a corrosion reaction? Provide some examples.
*24 g of zinc metal are dissolved in a 1 M HCl solution. How many coulombs have been produced by the anodic process?
If the previous reaction occurs over a thirty minute period, what current would have been produced?
*A sheet of carbon steel one meter wide by three meter long has lost 40 g to corrosion over the past six months. Convert that mass loss to a penetration rate of the steel in mm units. What would be the total corrosion current associated with such a corrosion rate? (carbon steel density = 7.8 g/cm3)
Repeat the previous problem for a sheet of aluminum A96061. (A96061 density = 2.7 g/cm3)
Chapter Four:Corrosion Thermodynamics (Visual aids)
Explain what is meant by 'the free energy of an electrochemical cell'.
*What is the significance of a negative cell potential?
Propose a simple experiment to estimate the entropy change (DS) associated with an electrochemical reaction.
Define the standard conditions associated with a gas? ... with a solid species? ... and with an ionic species?
Explain why it is much easier to use molarity instead of activity to describe the presence of an ionic species.
*Is it possible to use the power coming out of a half cell? Explain your answer.
Why are electrochemical cells described using typically two half cells?
Define the purpose of what is called the 1953 Stockholm convention in the context of electrochemistry.
*Rank the following ions in order of their thermodynamic ease of plating out of a solution: Cu2+, Ca2+, Fe2+, Fe3+, Na+, Pb2+, Fe3+, Cu+
*Rank the following elements in order of their thermodynamic ease of being oxidized in solution: Hg, Al, Fe, Au, Cr, Zn, Ag, Mg
*Using standard potentials and molarity for ion concentrations calculate the open circuit potential of the following electrochemical reactions (balance the equations with water related chemical species when necessary, i.e. H+, OH- and H2O):
H2O2 + Ni → H2O + Ni2+
H2O + Mg2+ → H2O2 + Mg
Ni + PbO2 → Pb2+ + Ni2+
Al3+ + OH- → Al + O2
*What does a measured potential value of 0.8 V vs. SHEwould be if the potential had been measured with a saturated silver chloride electrode? ... with a saturated copper sulfate electrode?
What does a measured potential value of -0.4 V vs. SCE would be if the potential had been measured with a saturated silver chloride electrode? ... with a saturated copper sulfate electrode?
Propose and explain your choice of a reference electrode for measuring the corrosion potential of a piece of metal buried in soil.
Propose and explain your choice of a reference electrode for measuring the corrosion potential of a piece of metal immersed in a very alkaline environment.
*What is the principle of a Luggin capillary and what are the main functions of such a device?
What is the electrochemical principle of a pH glass electrode?
What instrument would you use to measure directly the pH of a soil?
Can one predict the corrosion rate of a metal in a given environment with E-pH diagrams?
Can one predict which corrosion products will form on a metal in a given environment with E-pH diagrams?
*Some fuel cells operate by oxidizing hydrogen gas on an anode while reducing oxygen from ambient air in contact with a cathode. What would be the maximum voltage produced by such a cell running on pure hydrogen and air in an acidic environment? Would it be different if pure oxygen was used instead of ambient air?
Repeat question 21 for an alkaline environment.
Use the E-pH diagram for aluminum shown in Figure 4.13 to answer the following questions:
What are the aluminum dominant species at a potential of -0.5V vs. SHE and pH values of 2, 4, 6, 8, and 10?
Define the predominance domain of aluminum metallic element in terms of pH and potential.
Define the predominance domain of aluminum oxide in terms of pH and potential.
Would this aluminum oxide be protective on aluminum components? Please search the book to support your conclusion.
Use the E-pH diagram for iron shown in Figure 4.15 to answer the following questions:
What are the iron dominant species at a potential of -0.5V vs. SHE and pH values of 2, 4, 6, 8, and 10?
Define the predominance domain of iron metallic element in terms of pH and potential.
Define the predominance domain of rust or Fe(OH)3 in terms of pH and potential.
Would rust be protective on steel and iron? Please search the book to support your conclusion.
Chapter Five:Corrosion Kinetics and Applications of Electrochemistry to Corrosion (Visual aids)
Describe in your own words the significance of what is meant by 'overpotential'.
*What is the relation between the overpotential and standard potential of an electrochemical reaction?
*What is the relation between polarization and overpotential?
Describe the principles of a potentiodynamic scan.
Describe in your own words the significance of what is meant by the 'exchange current density' in reference to a corrosion reaction.
*Propose an alloy modification that would possibly disfavor the production of hydrogen at an electrode. ... and one that would favor it.
Would steel be a good electrode material for the production of hydrogen in an electrochemical cell? Considering what has been discussed in Chapter four would you suggest that such a process would be easier on the steel in an alkaline or an acidic environment?
What is the chemical significance of a polarization branch? Explain your answer.
*Describe a simple method to verify if an electrochemical reaction is limited by a concentration polarization effect.
*How many grams of dissolved oxygen are present in one liter of aerated water at 5ºC? ... at at 30ºC?
*Describe a simple method to reduce the quantity of dissolved oxygen in a water container or vessel.
Calculate the thickness of the Nernst diffusion layer for the electrochemical reduction of dissolved oxygen in water at 25ºC if the limited current density for that reaction is 0.01 mA/cm2. ... if it is 0.5 mA/cm2.
*Explain the main differences between the ohmic drop in an aqueous environment and the ohmic drop in an electrical conductor.
Can one use direct current to measure the ohmic drop in an electrochemical cell? Explain your answer.
How can a Luggin capillary improve the polarization measurement at an electrode?
Describe, in your own words, the methodology applied to estimate the ground resistivity for various soil depths.
What is the role of the two central pins in the Wenner method?
Describe the main advantages of each of the soil resistivity methods that have been used to measure soil resistivity.
Was is the purpose of graphing out an Evans diagram?
How does one determine the corrosion potential from a mixed potential diagram.
How does one determine the corrosion current from a mixed potential diagram.
Describe the main components required to carry out some electrochemical polarization tests.
Describe the main differences between potentiodynamic polarization, linear polarization resistance, and electrochemical impedance spectroscopy. Indicate what your arguments to propose one technique over another would be.
Provide some application examples of corrosion monitoring techniques, Highlighting the advantages and costs associated with these practices.
Describe the selection criteria that would make the choice of anodic protection a better choice than cathodic protection.
Describe two electrochemical techniques that are used in corrosion studies but not mentioned in the book. Explain their principles and main uses.
Chapter Six:Recognizing the Forms of Corrosion (Visual aids)
Search the Internet for examples to illustrate the inspectability of the forms of corrosion listed in the three groups described in pages 148 and 149.
*Corrosion problems can rarely be attributed to single forms of corrosion. Provide some examples to illustrate that statement.
*The seriousness of a corrosion situation is often directly related to the hidden nature of the specific corrosion defect that is progressing. Provide some examples in support of that statement.
The actual importance of a type of corrosion may greatly vary between affected systems. Provide some examples in support of that statement.
Provide some examples of uniform corrosion with pictures and general description.
*Where would general loss (uniform corrosion) be a concern. Provide examples and explanation.
Provide some examples of pitting corrosion with pictures and general description.
*Why would pitting corrosion be much more prone to provoke a catastrophic failure than uniform corrosion generally does?
Provide, from a basic search of the Internet, some details of the nature and chemistry of tubercles in water pipes.
Where might pitting undercutting be a serious design consideration?
Relate metallurgical features of a metallic material to the shapes of corrosion pits shown in Figure 6.11.
Elaborate on the three types of pitting that have been observed on copper in water service.
Why would stray currents be such a force to reckon with behind one of the most dramatic forms of pitting corrosion experienced in service? Use Faraday's law to support your arguments.
Propose a simple algorithm to estimate the pit density obtained from micrographs taken on corroded samples.
What would be the main purpose for using extreme value statistics for the evaluation of field coupons.
Use the pKa of the following hydroxides to predict the acidity in crevices formed on their respective metals: Cr(OH)3, Fe(OH)2, Sn(OH)4, Fe(OH)3, and Al(OH)3.
*Explain in your own words the role played by dissolved oxygen in the general mechanism proposed to explain the various steps in crevice corrosion.
Provide some examples of crevice corrosion different from those described in the book.
Extend the crevice corrosion scenario to situations encountered with non-metallic materials.
Why would it be misleading to call a galvanic corrosion process 'electrolysis', as many still refers to when discussing galvanic corrosion.
Why would the order of metals in galvanic series vary with environments? Explain your answer.
*Why would some metals, such as titanium for example, which are relatively easy to oxidize can still be found at the top of a galvanic series (Figure 6.31)?
Copper ions even in very low concentrations may deposit readily on an aluminum surface. First explain the deposition process itself before explaining why deposited copper nodules on the aluminum surface could lead to greatly accelerated corrosion of the aluminum material.
Explain why intergranular corrosion is often considered to be a localized form of galvanic corrosion.
Dealloying is in many ways similar to galvanic corrosion. Highlight the similarities and differences between these two technically different forms of corrosion.
Describe some field examples of hydrogen induced cracking and discuss some of the mechanisms that have been proposed to explain these problems.
How can hydrogen blistering be avoided?
Describe in simple words the main differences between laminar flow and turbulent flow in the context of velocity induced corrosion.
Flow accelerated corrosion is a particularly serious concern in the energy industry. Find some examples and cases to support that statement.
Provide some recommendations for the selection of an alloy to be used for the construction of a system handling high velocity seawater.
Provide a detailed mechanism invoking the collapse of bubbles to explain damage caused by cavitation corrosion.
Provide some recommendations for the selection of an alloy to be used for the construction of a system handling high levels of hydrogen sulfide in a low pH water.
Summarize the various characteristics and impact of the different types of cavitation that have been observed.
*Discuss the various types of stresses that can lead to SCC and highlight their importance with practical examples.
*Provide a few examples of events that may lead to the initiation of SCC.
Describe the consecutive steps that may occur when a SCC problem results in a full catastrophic failure, putting a special emphasis on the time scale involved in each of these steps.
Why is SCC generally described as an anodic process?
Are pure metals as susceptible to SCC as their alloys. Provide some examples.
Will fatigue corrosion affect metals and alloys that have usually a good endurance limit? Explain your answer.
Chapter Seven: Corrosion Failures, Factors, and Cells (Visual aids)
Describe situations where the forms of corrosion would be a better way of looking at problems and other cases where looking at factors leading to these corrosion problems would provide a better angle.
Provide some examples where each of the following factors would be of paramount importance in relation to aqueous corrosion: temperature, fluid velocity, impurities in the environment, presence of microbes, and presence of stray currents.
Provide some examples of what is referred to as 'nominal chemistry' and 'prior chemistry history' in the context of a location for analysis matrix.
*Propose some arguments to explain the high variance between expert opinions on the factors causing pitting corrosion (Figure 7.10).
Propose some useful applications of the survey results summarized in Figure 7.11.
*What is a corrosion cell and what are its main components?
Provide some examples of corrosion cells other than those described in the book.
*Can you imagine some corrosion cells that would be cancelling each other?
Figure 7.17 provides a detailed list of the factors causing galvanic corrosion. Discuss these factors using practical examples of galvanic corrosion. Specify the scientific nature of these factors and provide an indication of the importance of the role they play.
Find and discuss data related to the conductivity of the environments associated with the anchor support examples discussed in Chapter seven.
Estimate the potential gradients that may develop between various sections of a submerged steel pile. Assume that these gradients are caused by dissolved oxygen and use data provided in previous Chapters to justify your assumptions.
Compare and discuss the relative importance of each of the corrosion cell described in the book.
Can you think of any other corrosion cell besides those covered in the book?
*Describe the effects of corrosion stress cells in terms of energy release.
Provide a summary of the similarities and differences between what is called 'pack rust' and what some call 'pillowing'.
Provide some examples of surface film corrosion cells different than those described in the book.
*Provide some examples where microbes have been found to be the root cause of corrosion problems.
There are more than one pitting resistance number (PREN). Compare some of these numbers and discuss their relative importance.
Why is crevice corrosion said to be more preventable at the design stage than many other forms of corrosion?
*Can crevice corrosion degenerate in other forms of corrosion? Provide some examples.
*Why is it important to consider the electrical conductivity between various components when suspecting the presence of a galvanic corrosion problem?
The visualization of corrosion cells on freely corroding steel was an important achievement that permitted scientists to develop a better understanding of corrosion mechanisms at a time when instrumentation to do so was really minimal. Provide some examples of how such visual observations have led to modern corrosion protection schemes.
Chapter Eight: Corrosion by Water (Visual aids)
Provide some examples of water conditioning applications.
*Corrosion and the toxicity of potable water. Find and discuss various cases where corrosion processes have freed some toxic compounds in potable water.
Would the circulation of water aggravate or diminish the toxicity of the transported water? Explain and discuss your answer.
*Corrosion of waterworks is a major burden in many cities. Provide some examples.
Can the AWWA six step procedure shown in Figure 8.2 be easily adapted to the construction of new water handling systems? Explain your answer.
Elaborate on the condition assessment techniques described in section 8.2.3 highlighting the main differences between the assessment of metallic water pipes versus the assessment of prestressed concrete pipes.
Why would brackish waters be more corrosive than seawater?
Some freshwaters can be extremely corrosive. Provide some examples with details.
*Summarize the main elements that make natural fresh waters more or less corrosive.
Summarize the main elements that make seawater more or less corrosive.
Discuss the implications of the data presented in Figure 8.7 and compare these results with those presented in Figures 8.5 and 8.6.
Compare the corrosion rates as a function of pH reported for steel and aluminum to the information presented in the E-pH diagrams for the same metals (Chapter 4).
*Propose an explanation for the maximum in corrosion rate reported in Figure 8.9.
What is the conductivity of seawater containing the equivalent of 3.5% KCl? ... 2.5% KCL?
Discuss the main changes that have have happened in the cooling water industry during recent years. Put a particular emphasis on the changes that have been introduced in relation to environmental concerns.
Discuss the importance of acid cleaning of industrial heat exchangers making particular reference to the energy costs associated with running medium to high temperature processes.
Supercritical water possesses special characteristics that may require particular attention from a corrosion engineering standpoint. Explain and discuss.
Nuclear energy would be a much easier political choice if it was not for the history of accidents the industry has suffered in recent history. Discuss some of these accidents making a particular reference to the role played by corrosion.
A great amount of efforts have been spent to monitor the quality of water in pressurized water reactors. Describe some of the monitoring techniques used by the industry and discuss the value of the information collected.
Discuss the importance of water treatments and compare the advantages and disadvantages of the various methods currently used in industry.
Why would water demineralization be an important issue in energy production plants?
Examples of corrosion inhibitors are presented in Table 8.14. Find additional examples that illustrate the usefulness of corrosion inhibitors and discuss the merit of these in these applications.
What is the relation between the hardness of a water and the ion activity product described on page 313?
*What is the physical significance of a water that has a SL value smaller than 1.0? ... and one that has a SL value larger than 1.0?
*Calculate the LSI of a water with a pH of 5.2 and a TDS of 450 mg/L knowing that the concentrations of calcium and magnesium ions in this water are respectively 200 and 22 mg/L.
Summarize the differences between the scaling indices presented in the book and high light applications where these indices would be most appropriate.
What are the pros and cons of using calculations using the ion association model presented on pages 318 to 327.
Chapter Nine: Atmospheric Corrosion (Visual aids)
Provide and discuss some visible examples of atmospheric corrosion.
Atmospheric corrosion may sometimes produce some interesting effects. Provide some examples.
*Are industrial sites near where you live more corrosive than adjacent locations? Provide some examples.
*Indoor corrosion has caused many unpleasant surprises. Find some examples close to your immediate surrounding.
Examine the case described on pages 336 and 337. Do you agree with the analysis provided? Would similar cases be possible where you live?
*The depression of the critical humidity levels on a metallic surface may seriously limit the use of some materials in various applications. Propose some design solutions to limit or avoid altogether such problems.
*Calculate the dew point temperature for a RH of 45% when the ambient temperature is 22oC? ... when it is 26oC?
Sulfur dioxide is a common pollutant with a great impact on atmospheric corrosion. Identify common sources of this pollutant and provide a brief description on how it is generated at these sources.
Does the size of aerosol particles matter in the context of corrosion processes?
Provide a summary of possible solutions to either reduce the use of deicing salts on winter roads or to altogether replace the chlorides by alternate but less corrosive salts.
Some examples of corrosion due to deicing salts are provided in the book. Find and document additional examples.
The Sereda sensor can provide a measure of the TOW. Demonstrate through calculations of surface film resistance how this device would work in realistic conditions.
Why would subfloor environments be more corrosive than other locations around or in a New Zealand dwelling (refer to the work described on pages 351 to 353).
Making direct corrosivity measurements is the ideal method to investigate the corrosivity of a given environment. Propose and discuss new ways to carry out such measurements.
Do you agree with the assessment of the corrosion factors made from the results summarized in Figure 9.30? Explain your answer.
The assessment of environmental severity is a modern approach to help equipment operators to manage atmospheric corrosion problems. Propose a scenario for the implementation of such an approach in the environment of your choice.
Discuss the algorithm described in Figure 9.31.
What is the relation between the time-of-wetness (TOW) concept used in the ISO 9223 framework and RH?
*The ISO 9223 standard indicates that should be no corrosion at temperature below 0oC. Independent researchers have however proposed to lower this minimum temperature to lower values in order to account for the actual corrosion observed in Nordic climates. provide an explanation for the observed corrosion at temperature below the freezing point.
Corrosivity maps: describe some applications for such maps.
The orientation and direction of exposure of the specimens are important considerations when carrying out atmospheric corrosion tests. Explain how you could use this sensitivity to your advantage.
How shading could influence the results of an atmospheric corrosion exposure?
Find in your neighbourhood some structural elements made of weathering steel and report on their state and condition.
Why would crevice corrosion be the Achilles heel of weathering steel? Provide a scientific explanation.
Find in your neighbourhood some structural elements made of stainless steel and report on their state and condition.
Flying with stainless steel airplanes became historical when processes to manufacture high strength aluminum alloys became available. Compare the specific strength of these two types of materials.
*Find in your neighbourhood some structural elements made of copper and copper alloys and report on their state and condition.
Find in your neighbourhood some structural elements made of aluminum and report on their state and condition.
*Find in your neighbourhood some structural elements made of galvanized steel and report on their state and condition.
*Use one of the corrosivity maps presented in the book to specify the thickness required of a galvanized coating to achieve a useful life of fifty years in the various environments described on that map.
Find in your neighbourhood some structural elements made of polymeric material (plastic) and report on their state and condition.
Chapter Ten: Corrosion in Soils and
Microbiologically Influenced Corrosion
High Temperature Corrosion
Chapter Eleven:Materials Selection, Testing and Design Considerations (Visual aids)
Chapter Twelve:Corrosion as a Risk (Visual aids)
Chapter Thirteen:Cathodic Protection (Visual aids)
Chapter Fourteen: Protective Coatings(Visual aids)
Chapter Fifteen: High Temperature Corrosion(Visual aids)
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