1. 1
   A marine engineer inspects an old steel ship's hull that has been left in a dry dock for several months, exposed to damp sea air. Patches of a reddish-brown flaky substance have formed on unpainted areas of the hull, while painted areas remain unaffected.

   (a)

   Which two substances must both be present for this reddish-brown substance to form on the steel?

   [1 mark]

   • AOxygen and water
   • BCarbon dioxide and water
   • COxygen and nitrogen
   • DWater and salt only

   (b)

   What is the chemical name of the reddish-brown flaky substance formed on the unpainted steel?

   [1 mark]

   • AAnhydrous iron(III) oxide
   • BIron(II) sulfate
   • CIron(III) chloride
   • DHydrated iron(III) oxide

   (c)

   Explain why the painted areas of the hull have not corroded, referring to the conditions needed for rusting.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A historian studying a Victorian-era water pipe network finds that iron pipes coated with a thin layer of zinc have survived over a century underground with little corrosion, even where the zinc coating has been chipped away by tree roots. Iron pipes without any coating, buried in the same soil, are almost completely corroded away.

   (a)

   What is the name of the process used to coat the iron pipes with zinc?

   [1 mark]

   • AElectrolysis of brine
   • BAnodising
   • CGalvanising
   • DThermal decomposition

   (b)

   Which statement correctly explains why the zinc-coated iron pipe still resists rusting even where the zinc coating has been chipped, exposing the iron underneath?

   [1 mark]

   • AZinc is less reactive than iron and forms a layer of rust that blocks water
   • BZinc is more reactive than iron and loses electrons in preference to iron, protecting it
   • CZinc reacts with oxygen to form a gas that pushes water away from the pipe
   • DZinc dissolves in groundwater and makes the water too alkaline for rusting to occur

   (c)

   Describe, in terms of electron loss, why the zinc is described as giving 'sacrificial protection' to the iron pipe.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A car manufacturer is deciding how to protect the steel body panels of a new car model from rusting.

   (a)

   Describe three different barrier methods that could be used to prevent the steel body panels from rusting, and explain how a barrier method works to prevent rusting in general.

   [3 marks]

   (b)

   The manufacturer is also considering galvanising some steel components, such as exhaust brackets, instead of only painting them. Explain why galvanising can offer better long-term protection against rusting than painting alone, including what happens if the galvanised coating becomes scratched during use.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A museum conservator is restoring a collection of wrought-iron garden gates dating from the 19th century, currently showing extensive rusting after decades stored in a damp outdoor shed. The conservator must choose a long-term protection strategy before returning the gates to outdoor display.

   (a)

   Discuss the conditions required for rusting, and explain how different barrier methods (painting, greasing, plastic coating) and galvanising could each be used to protect the restored gates, comparing their suitability for gates that will be handled and repositioned outdoors.

   [6 marks]

   (b)

   The conservator also wants to explain the science of the restoration to museum visitors in a public display. Write an explanation, suitable for visitors, describing what rust is chemically, the two conditions needed for it to form, and why a lightly rusted but galvanised modern replica gate placed alongside the original would be expected to last far longer outdoors without maintenance than the original ungalvanised wrought iron.

   [6 marks]

   Total for question 4: 12 marks

End of questions