When a metal corrodes A the metal reacts with nitrogen B the metal reacts with another metal C the metal element decomposes D the metal is oxidised (b) An experiment is carried out to see if magnesium ribbon wrapped around a piece of iron rod has an effect on the rate at which the iron rod rusts - Edexcel - GCSE Chemistry - Question 7 - 2019 - Paper 1

The iron rod is used rather than a stainless steel rod because iron is more susceptible to corrosion. In this experiment, the focus is on observing how rust forms on the iron rod, and using stainless steel, which is known for its corrosion resistance, would not produce visible rusting. Therefore, the experiment requires a material that will corrode more readily, making iron the suitable choice.