In marine engineering, sacrificial anodes are commonly attached to the steel hulls of ships to prevent the corrosion of iron in seawater.
Which metal is suitable for use as a sacrificial anode, and what is the correct explanation for its protective action?
Copper, because it is less reactive than iron and will prevent the iron from losing electrons by acting as an electron sink.
Zinc, because it is more reactive than iron and will be preferentially oxidised, supplying electrons to the iron hull.
Tin, because it is more reactive than iron and will undergo sacrificial oxidation to form a self-healing barrier of tin(II) oxide.
Silver, because it is highly unreactive and will transfer electrons to iron ions to reduce them back to metallic iron.
Practise Edexcel GCSE Chemistry Transition metals, alloys and corrosion with exam-style questions for Foundation and Higher tier. 97 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
