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EASY What is a necessary condition for galvanic corrosion to occur?

  • When two identical metals contact each other
  • When two dissimilar metals contact each other and are surrounded by an electrolyte (correct)
  • When a metal is exposed to water
  • When a metal is exposed to air

    • What happens to the anodic metal in a galvanic corrosion process?

  • It loses electrons and soluble metal ions are left behind (correct)
  • It gains electrons and becomes more noble
  • It remains unchanged
  • It becomes more reactive

    • What is the role of the electrolyte in galvanic corrosion?

  • To provide an electric field
  • To accelerate the corrosion process
  • To provide a pathway for electrons to flow (correct)
  • To separate the two metals

    • What determines the rate of corrosion in galvanic corrosion?

    <p>The potential difference between the two metals</p> Signup and view all the answers

    What is the electromotive series?

    <p>A list of metals in order of their electrochemical potential</p> Signup and view all the answers

    What happens when a metal is under stress, such as in a bend or dent?

    <p>It becomes more anodic</p> Signup and view all the answers

    Why do noble metals not readily corrode?

    <p>Because they have a high electrochemical potential</p> Signup and view all the answers

    What is stress corrosion cracking?

    <p>A type of corrosion that occurs in areas under stress, such as bends or dents</p> Signup and view all the answers

    Which metal has the highest electrochemical potential?

    <p>Gold</p> Signup and view all the answers

    What is the purpose of a sacrificial anode?

    <p>To protect other metals from corrosion</p> Signup and view all the answers

    What is the electrochemical potential of hydrogen?

    <p>0.00 V</p> Signup and view all the answers

    What is the result of the reaction at the cathode in a zinc-copper galvanic cell?

    <p>Formation of H2 gas</p> Signup and view all the answers

    What is the rule of thumb for the electrochemical potential difference between two materials to minimize galvanic corrosion?

    <p>Less than 0.15 V</p> Signup and view all the answers

    What is the purpose of monitoring closed loop corrosion?

    <p>To identify areas of high corrosion</p> Signup and view all the answers

    What is the purpose of corrosion coupons?

    <p>To monitor corrosion rates</p> Signup and view all the answers

    What is the result of the reaction at the anode in a zinc-copper galvanic cell?

    <p>Formation of Zn2+ cations</p> Signup and view all the answers

    What is the purpose of using borescopes in closed system corrosion monitoring?

    <p>To inspect the inside of tubes and shells for signs of corrosion</p> Signup and view all the answers

    MEDIUM What is the purpose of checking pressure drops and flow rates across heat exchangers and strainers?

    <p>To identify corrosion or deposition</p> Signup and view all the answers

    What is the reason for galvanic corrosion occurrence even when there is only one type of metal present?

    <p>All of the above</p> Signup and view all the answers

    What happens to the anodic metal in a galvanic corrosion process when it loses electrons?

    <p>Soluble metal ions are left behind</p> Signup and view all the answers

    What determines the direction of electron flow between two metals in a galvanic cell?

    <p>Electrochemical potential difference</p> Signup and view all the answers

    What is the purpose of the electromotive series?

    <p>To show the voltage difference between metals in a galvanic cell</p> Signup and view all the answers

    What happens in stress corrosion cracking?

    <p>The area under stress becomes more anodic</p> Signup and view all the answers

    Why do noble metals not readily corrode?

    <p>Because they receive electrons from anodic metals</p> Signup and view all the answers

    What is the correlation between the electrochemical potential difference and the rate of corrosion?

    <p>The greater the potential difference, the faster the rate of corrosion</p> Signup and view all the answers

    What is the role of the electrolyte in galvanic corrosion?

    <p>To provide a pathway for ions to move</p> Signup and view all the answers

    In a galvanic corrosion process, which of the following ions are involved in the reaction at the cathode?

    <p>H+ and OH-</p> Signup and view all the answers

    What is the primary reason for using sacrificial anodes in a galvanic corrosion process?

    <p>To reduce the corrosion rate of the cathode</p> Signup and view all the answers

    Which of the following metals would be the most effective sacrificial anode in a galvanic corrosion process?

    <p>Lithium</p> Signup and view all the answers

    What is the purpose of monitoring pH in closed system corrosion monitoring?

    <p>To adjust the corrosion inhibitor residual in the system</p> Signup and view all the answers

    What is the result of the reaction at the anode in a zinc-copper galvanic cell?

    <p>Formation of zinc hydroxide</p> Signup and view all the answers

    Which of the following is a common method for preventing galvanic corrosion in industrial applications?

    <p>Electrically insulating dissimilar metals</p> Signup and view all the answers

    What is the purpose of checking pipes and piping connections for leaks in closed system corrosion monitoring?

    <p>To identify areas where corrosion is most likely to occur</p> Signup and view all the answers

    What is the role of oxygen scavengers in closed system corrosion monitoring?

    <p>To remove oxygen from the system to prevent corrosion</p> Signup and view all the answers

    Which of the following is a common method for monitoring corrosion in closed systems?

    <p>Using corrosion coupons</p> Signup and view all the answers

    What is the primary reason for replacing dissimilar piping with piping of similar materials in closed system corrosion monitoring?

    <p>To prevent galvanic corrosion</p> Signup and view all the answers

    HARD What is the primary reason why a pipe made of a single material can still undergo galvanic corrosion?

    <p>Surface imperfections and crystal misalignment create differences in electrochemical potential</p> Signup and view all the answers

    What happens to the anodic metal when it loses electrons in a galvanic corrosion process?

    <p>Soluble metal ions are left behind and enter the electrolyte</p> Signup and view all the answers

    What is the primary reason why zinc is often used as a sacrificial anode in galvanic corrosion prevention?

    <p>Because it has a low electrochemical potential</p> Signup and view all the answers

    What is the role of conductivity testing in closed system corrosion monitoring?

    <p>To detect corrosion potential</p> Signup and view all the answers

    What is the primary reason why noble metals do not readily corrode?

    <p>They have a low electrochemical potential and are less reactive</p> Signup and view all the answers

    What is the correlation between the electrochemical potential difference and the rate of corrosion in galvanic corrosion?

    <p>The greater the electrochemical potential difference, the faster the rate of corrosion</p> Signup and view all the answers

    What is the purpose of using borescopes in closed system corrosion monitoring?

    <p>To inspect the inside of tubes and shells for signs of corrosion or deposition</p> Signup and view all the answers

    What is the correlation between the electrochemical potential difference and the rate of corrosion?

    <p>A higher electrochemical potential difference results in faster corrosion</p> Signup and view all the answers

    What is the primary reason why a metal under stress, such as in a bend or dent, is more susceptible to corrosion?

    <p>The metal is more anodic and has a higher electrochemical potential difference with the surrounding metal</p> Signup and view all the answers

    What is the primary purpose of the electromotive series?

    <p>To compare the electrochemical potential of different metals</p> Signup and view all the answers

    Why is it important to replace dissimilar piping with piping of similar materials in closed system corrosion monitoring?

    <p>To prevent galvanic corrosion</p> Signup and view all the answers

    What is the purpose of monitoring oxygen scavenger residuals in closed system corrosion monitoring?

    <p>To prevent oxygen-related corrosion</p> Signup and view all the answers

    What is the role of the electrolyte in galvanic corrosion?

    <p>To provide a pathway for ions to move between the anode and cathode</p> Signup and view all the answers

    What is the primary reason why a scratch or dent can cause galvanic corrosion in a metal?

    <p>The scratch or dent creates a area of low electrochemical potential</p> Signup and view all the answers

    What is the primary reason for using corrosion coupons in closed system corrosion monitoring?

    <p>To monitor corrosion rates</p> Signup and view all the answers

    What is the role of corrosion inhibitors in closed system corrosion monitoring?

    <p>To reduce the corrosion rate</p> Signup and view all the answers

    What is the purpose of checking pipes and piping connections for leaks in closed system corrosion monitoring?

    <p>To detect potential corrosion sites</p> Signup and view all the answers

    What is the result of the reaction at the cathode in a zinc-copper galvanic cell?

    <p>The release of hydrogen gas</p> Signup and view all the answers

    Study Notes

    Galvanic Corrosion

    • Occurs when two dissimilar metals contact each other in an electrolyte (an aqueous solution)
    • Each metal has a characteristic electrochemical potential, causing electrons to flow from the more negative metal (anode) to the more positive metal (cathode)

    Anode and Cathode

    • Anode loses electrons, leaving behind soluble metal ions that enter solution with the electrolyte, causing corrosion
    • Cathode receives electrons, resulting in a build-up of hydrogen gas

    Electrochemical Potential

    • The difference in electrochemical potential between two metals causes galvanic corrosion
    • Electrochemical potential is listed in the electromotive series (Table 2)
    • Metals at the top of the table are the most cathodic (noble) and do not readily corrode

    Galvanic Cell

    • A galvanic cell consists of two metals with different electrochemical potentials, surrounded by an electrolyte
    • The greater the potential difference between the two metals, the greater the rate of corrosion

    Corrosion Process

    • Electrons flow from the anode to the cathode, creating ions that enter solution with the electrolyte
    • At the cathode, electrons combine with hydrogen ions to form hydrogen gas
    • At the anode, metal ions combine with hydroxide ions to form a precipitate

    Preventing Galvanic Corrosion

    • Use materials with similar electrochemical potentials
    • Electrically insulate dissimilar metals
    • Use sacrificial anodes to protect more noble metals
    • Regularly replace sacrificial anodes

    Monitoring Closed Loop Corrosion

    • Use instruments to monitor corrosion or system corrosiveness
    • Perform visual inspections and checks to determine active corrosion sites
    • Remove and examine corrosion coupons on a regular basis
    • Inspect the integrity of sacrificial anodes
    • Perform tests on closed system water to determine pH, oxygen scavenger residual, conductivity, and corrosion inhibitor residual

    Preventing Closed System Corrosion

    • Replace dissimilar piping with piping of similar materials
    • Install special dielectric pipe fittings if piping connections between dissimilar metals are unavoidable
    • Install sacrificial anodes and replace them regularly
    • Add corrosion inhibitor and oxygen scavenger according to plant water treatment recommendations

    Galvanic Corrosion

    • Occurs when two dissimilar metals contact each other in an electrolyte (an aqueous solution)
    • Each metal has a characteristic electrochemical potential, causing electrons to flow from the more negative metal (anode) to the more positive metal (cathode)

    Anode and Cathode

    • Anode loses electrons, leaving behind soluble metal ions that enter solution with the electrolyte, causing corrosion
    • Cathode receives electrons, resulting in a build-up of hydrogen gas

    Electrochemical Potential

    • The difference in electrochemical potential between two metals causes galvanic corrosion
    • Electrochemical potential is listed in the electromotive series (Table 2)
    • Metals at the top of the table are the most cathodic (noble) and do not readily corrode

    Galvanic Cell

    • A galvanic cell consists of two metals with different electrochemical potentials, surrounded by an electrolyte
    • The greater the potential difference between the two metals, the greater the rate of corrosion

    Corrosion Process

    • Electrons flow from the anode to the cathode, creating ions that enter solution with the electrolyte
    • At the cathode, electrons combine with hydrogen ions to form hydrogen gas
    • At the anode, metal ions combine with hydroxide ions to form a precipitate

    Preventing Galvanic Corrosion

    • Use materials with similar electrochemical potentials
    • Electrically insulate dissimilar metals
    • Use sacrificial anodes to protect more noble metals
    • Regularly replace sacrificial anodes

    Monitoring Closed Loop Corrosion

    • Use instruments to monitor corrosion or system corrosiveness
    • Perform visual inspections and checks to determine active corrosion sites
    • Remove and examine corrosion coupons on a regular basis
    • Inspect the integrity of sacrificial anodes
    • Perform tests on closed system water to determine pH, oxygen scavenger residual, conductivity, and corrosion inhibitor residual

    Preventing Closed System Corrosion

    • Replace dissimilar piping with piping of similar materials
    • Install special dielectric pipe fittings if piping connections between dissimilar metals are unavoidable
    • Install sacrificial anodes and replace them regularly
    • Add corrosion inhibitor and oxygen scavenger according to plant water treatment recommendations

    Galvanic Corrosion

    • Occurs when two dissimilar metals contact each other in an electrolyte (an aqueous solution)
    • Each metal has a characteristic electrochemical potential, causing electrons to flow from the more negative metal (anode) to the more positive metal (cathode)

    Anode and Cathode

    • Anode loses electrons, leaving behind soluble metal ions that enter solution with the electrolyte, causing corrosion
    • Cathode receives electrons, resulting in a build-up of hydrogen gas

    Electrochemical Potential

    • The difference in electrochemical potential between two metals causes galvanic corrosion
    • Electrochemical potential is listed in the electromotive series (Table 2)
    • Metals at the top of the table are the most cathodic (noble) and do not readily corrode

    Galvanic Cell

    • A galvanic cell consists of two metals with different electrochemical potentials, surrounded by an electrolyte
    • The greater the potential difference between the two metals, the greater the rate of corrosion

    Corrosion Process

    • Electrons flow from the anode to the cathode, creating ions that enter solution with the electrolyte
    • At the cathode, electrons combine with hydrogen ions to form hydrogen gas
    • At the anode, metal ions combine with hydroxide ions to form a precipitate

    Preventing Galvanic Corrosion

    • Use materials with similar electrochemical potentials
    • Electrically insulate dissimilar metals
    • Use sacrificial anodes to protect more noble metals
    • Regularly replace sacrificial anodes

    Monitoring Closed Loop Corrosion

    • Use instruments to monitor corrosion or system corrosiveness
    • Perform visual inspections and checks to determine active corrosion sites
    • Remove and examine corrosion coupons on a regular basis
    • Inspect the integrity of sacrificial anodes
    • Perform tests on closed system water to determine pH, oxygen scavenger residual, conductivity, and corrosion inhibitor residual

    Preventing Closed System Corrosion

    • Replace dissimilar piping with piping of similar materials
    • Install special dielectric pipe fittings if piping connections between dissimilar metals are unavoidable
    • Install sacrificial anodes and replace them regularly
    • Add corrosion inhibitor and oxygen scavenger according to plant water treatment recommendations

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    Description

    Learn about the process of galvanic corrosion, where two dissimilar metals in contact with an electrolyte cause electrons to flow, resulting in corrosion.

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