Chemical Attack on Aircraft Materials Quiz
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Questions and Answers

What is the chemical process through which mercury attacks aluminium?

  • Oxidation
  • Electrolysis
  • Amalgamation (correct)
  • Decomposition
  • In what way does mercury attack aluminium along grain boundaries?

  • Periodically
  • Indiscriminately
  • Slowly
  • Rapidly (correct)
  • Why does the anode give up electrons more easily when it is smaller than the cathode?

  • Due to decreased surface area
  • Due to higher electron density
  • Due to lower electron density
  • Due to increased surface area (correct)
  • What effect does the chemical reaction of mercury on aluminium have in an aeroplane?

    <p>Complete destruction of aluminium</p> Signup and view all the answers

    Which of the following metals is NOT commonly found in any quantity around aircraft?

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

    What is the corrosion product of aluminium?

    <p>White-to-grey powdery material</p> Signup and view all the answers

    What is the protective coating applied to some aluminium parts?

    <p>Aluminium oxide film</p> Signup and view all the answers

    What is the effect of anodising on the thickness of the oxide film on aluminium?

    <p>Increases the thickness</p> Signup and view all the answers

    What should be avoided to prevent unnecessary destruction of an anodised surface?

    <p>Nicks and scratches</p> Signup and view all the answers

    Which metal is noted for being highly susceptible to corrosion when exposed without a protective finish?

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

    What happens to magnesium corrosion deposits over time?

    <p>They raise slightly and spread rapidly</p> Signup and view all the answers

    What is the main cause of fretting corrosion?

    <p>Destruction of the protective film by rubbing action</p> Signup and view all the answers

    In fretting corrosion, why does debris act as an abrasive?

    <p>It gets trapped between surfaces due to minimal movement</p> Signup and view all the answers

    How is fretting corrosion visually signaled around rivets in a skin?

    <p>Dark deposits around the rivet heads</p> Signup and view all the answers

    What distinguishes exfoliation corrosion from other forms of corrosion?

    <p>It mainly occurs in extruded materials with laminar grain structure</p> Signup and view all the answers

    What is a characteristic feature of exfoliation corrosion?

    <p>'Peeling away' effect along grain boundaries</p> Signup and view all the answers

    Why does exfoliation corrosion primarily affect extruded materials?

    <p>Due to their laminar grain structure</p> Signup and view all the answers

    What is the purpose of cadmium as a coating on high-strength steel parts?

    <p>To improve resistance to corrosion fatigue</p> Signup and view all the answers

    How can one identify corrosion on cadmium plating?

    <p>By the presence of white-to-brown-to-black mottling on the surface</p> Signup and view all the answers

    In what way does chromium protect underlying metal when used as a protective plating?

    <p>By forming a continuous oxide coating</p> Signup and view all the answers

    What is the protective function of chromium coatings with cracks?

    <p>It still protects the base metal below these separations</p> Signup and view all the answers

    What happens when cadmium is coupled with steel in terms of galvanic action?

    <p>It protects the steel by galvanic action</p> Signup and view all the answers

    How does cadmium behave when it shows mottling and cracks in the plating?

    <p>It still performs its protective function as an anodic material</p> Signup and view all the answers

    What causes the tarnish on silver surfaces?

    <p>Silver sulphide</p> Signup and view all the answers

    In what way does gold provide benefit when used as a coating?

    <p>Improved corrosion resistance and solderability</p> Signup and view all the answers

    How does the tarnish on silver surfaces affect circuit electrical characteristics?

    <p>Does not affect electrical characteristics</p> Signup and view all the answers

    What material is silver usually plated over in circuits?

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

    What accelerates the corrosion of copper when silver is plated over it?

    <p>Galvanic action</p> Signup and view all the answers

    What color does tarnish on silver surfaces typically appear as?

    <p>Brown-to-black</p> Signup and view all the answers

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