Worksheet: Prevention of Rusting

In this worksheet, we will practice describing methods for the prevention of rusting in iron and identifying metals less susceptible to oxide formation.

Q1:

The Statue of Liberty in New York City contains a copper skin wrapped around iron supports. Why is this design problematic?

  • ACopper develops a thick oxide layer, preventing it from acting as a sacrificial coating for the iron support.
  • BCopper cannot form an alloy with iron, so the iron support is exposed to rusting.
  • CCopper has a low tensile strength so it cracks easily, exposing the iron support to rusting.
  • DCopper is less reactive than iron, so it accelerates rusting of the iron support.
  • ECopper binds water more strongly than iron, so it accelerates rusting of the iron support.

Q2:

Which of the following is not a method for lowering the rate of rusting?

  • AGreasing
  • BAlloying
  • CElectroplating
  • DWelding
  • EGalvanization

Q3:

Vehicle components are sometimes made of aluminum instead of steel in order to reduce the risk of oxidation.

Why is aluminum less susceptible than steel to oxidation?

  • AAluminum binds water less strongly than steel.
  • BAluminum is less reactive than steel.
  • CAluminum is protected by an unreactive carbonate layer.
  • DAluminum is protected by an unreactive oxide layer.
  • EAluminum forms cracks less easily than steel.

Which of the following is another advantage of using aluminum instead of steel in vehicle components?

  • AAluminum is less dense than steel.
  • BAluminum has a higher melting point than steel.
  • CAluminum is harder than steel so it scratches less easily.
  • DAluminum is stronger than steel so it deforms less easily.
  • EAluminum is less expensive than steel.

Q4:

Iron may be protected from rusting by supplying the metal with an electric current. Why does this method lower the risk of rusting?

  • AThe supply of electrons promotes the formation of a protective surface oxide layer.
  • BThe supply of electrons converts oxygen to water, preventing it from acting as an oxidant.
  • CThe supply of electrons causes the iron surface to become charged, binding protective surface oxides more strongly.
  • DThe supply of electrons converts iron ions back to metallic iron.
  • EThe supply of electrons causes the iron surface to become charged, binding oxygen molecules less strongly.

Q5:

An iron surface is protected from rusting by coating it with a sacrificial metal from a salt solution. Which process is responsible for the formation of the protective layer?

  • AOxidation of dissolved metal ions by an electric current
  • BReaction of dissolved metal ions with the iron surface
  • CReaction of dissolved metal ions with surface iron oxides
  • DReduction of dissolved metal ions by an electric current
  • EReaction of dissolved metal ions with atmospheric oxygen

Q6:

Which of the following is not a useful property in sacrificial metal coatings for steel objects?

  • AHigh tensile strength
  • BHigh hydrophobicity
  • CLow density
  • DLow reactivity
  • EHigh melting point

Q7:

What is the main reason for preferring oil over plastic as a protective coating for a steel bicycle chain?

  • AOil is less expensive than a plastic coating.
  • BThe oil layer reduces oxidation by acting as a sacrificial coating.
  • COil is less likely to react with the steel chain.
  • DOil can spread to maintain a uniform coating during movement of the chain.
  • EOil is less heavy than plastic so is less likely to impede the chain movement.

Q8:

A steel vehicle is protected from rusting by spraying the exposed surface with a second metal.

What name is given to this process?

  • APainting
  • BElectroplating
  • CPassivation
  • DGalvanization
  • EAlloying

What name is given to the protective metal layer?

  • ASacrificial anode
  • BAlloy
  • CPassivating layer
  • DSacrificial cathode
  • EElectrical insulation

Q9:

Which of the following is the best definition of galvanic corrosion?

  • AOxidation of a metal accelerated by alloying
  • BOxidation of a metal accelerated by the presence of a more reactive metal
  • CReduction of a metal accelerated by the presence of a less reactive metal
  • DOxidation of a metal accelerated by the presence of a less reactive metal
  • EReduction of a metal accelerated by alloying

Q10:

Which of the following is the best definition of passivation?

  • AProtection of a metal surface by an unreactive plastic layer
  • BProtection of a metal surface by a sacrificial material
  • CProtection of a metal surface by an electrical current
  • DProtection of a metal surface by an unreactive oxide layer
  • EProtection of a metal surface by an unreactive oil layer

Q11:

Which term best describes the protective material used in cathodic protection?

  • APassivating layer
  • BSacrificial cathode
  • CAlloy
  • DSacrificial anode
  • EHydrophobic layer

Q12:

Which of the following is not a useful property in protective oil coatings for moving steel components?

  • ALow reactivity
  • BLow volatility
  • CHigh hydrophobicity
  • DHigh viscosity
  • ELow melting point

Q13:

Which of the following is not a useful property in protective plastic coatings for moving steel components?

  • AHigh elasticity
  • BLow weight
  • CHigh yield point
  • DLow melting point
  • EHigh hydrophobicity

Q14:

Which of the following metals could be used as a sacrificial coating on iron to prevent rust formation?

  • A P b
  • B S n
  • C C u
  • D A l
  • E P t

Q15:

Which of the following could not be used as a sacrificial metal to prevent corrosion of tin?

  • AAluminum
  • BMagnesium
  • CZinc
  • DLead
  • EIron

Q16:

An electrochemical cell is constructed by connecting plates of iron and copper to a voltmeter and immersing the plates in separate salt solutions linked via a salt bridge. Ferroxyl indicator is added to each of the two solutions. Which of the following images best illustrates the colors of the solutions at the end of this experiment? Note that the salt bridges are omitted for clarity.

  • A
    V F erroxyl Indicator F e C u
  • B
    V F erroxyl Indicator F e C u
  • C
    V F erroxyl Indicator F e C u
  • D
    V F erroxyl Indicator F e C u
  • E
    V F erroxyl Indicator F e C u

Q17:

A steel can is protected by coating it with a layer of tin. Part of the steel surface is exposed through a scratch in the tin layer, as shown. How does the rate of rusting of the steel exposed by the scratch compare with that of uncoated steel?

  • AThe exposed steel rusts at the same rate as uncoated steel.
  • BThe exposed steel rusts but more slowly than uncoated steel.
  • CThe exposed steel does not rust, unlike uncoated steel.
  • DThe exposed steel rusts more rapidly than uncoated steel.
  • EIron in the steel reacts with tin to form a new protective layer, so no steel is exposed.

Q18:

The diagram illustrates an iron plate that has been protected from rusting by galvanization of the exposed surface.

Identify the material usually present in the protective coating X .

  • ACopper
  • BTin
  • CPlastic
  • DZinc
  • EOil

When intact, how does the coating protect the iron plate?

  • AThe coating physically prevents oxygen and water from reaching the iron plate.
  • BThe coating binds water to prevent it from reaching the iron plate.
  • CThe coating reacts with rust to convert it back to metallic iron.
  • DThe coating reacts with oxygen to prevent it from reaching the iron plate.
  • EThe coating traps rust to prevent it from flaking away.

If the coating is scratched, how does it continue to protect the iron plate?

  • AThe coating cannot protect the iron plate if scratched.
  • BThe coating flows to fill the scratch.
  • CThe coating is oxidized instead of the iron plate.
  • DThe coating absorbs water and expands to fill the scratch.
  • EThe coating reacts with the exposed iron to form a rust-resistant alloy.

Q19:

A steel oil pipeline is protected via an electrical connection to a buried block of sacrificial metal. Which diagram correctly illustrates the composition of the sacrificial metal and the direction of the electrical current?

  • A
  • B
  • C
  • D
  • E

Q20:

Based on their positions on the reactivity series, and their densities, which of the following metals would produce the lightest sacrificial coating for a lead object?

  • ACopper
  • BNickel
  • CTin
  • DZinc
  • EIron

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