Two steel flood-barrier panels are exposed to air and rainwater.
Panel P is painted. Panel Z is coated with zinc. On both panels, the coating is scratched through to the steel.
The table shows the total mass of zinc coating on panel Z.
| Time in years | Mass of zinc coating in kg |
|---|---|
| 0 | 3.20 |
| 5 | 2.30 |
The zinc coating is renewed when its mass falls to 0.50 kg. Assume that the zinc is lost at a constant rate.
Explain which panel is likely to rust at the scratch.
Calculate how many years after installation the zinc coating should be renewed.
Show your working.
118 exam-style questions on AQA GCSE Chemistry 10.3 Using materials, covering 10.3.1 Corrosion and its prevention, 10.3.2 Alloys as useful materials, and 10.3.3 Ceramics, polymers and composites. Each one has a worked solution and a mark scheme showing where the marks go.