Zinc washers are fitted in contact with steel screws used on outdoor wooden furniture. Most of the surface of each steel screw remains uncovered.
Zinc is more reactive than iron.
The table shows the results after one year.
| Observation | At the start | After one year |
|---|---|---|
| Total mass of zinc washers | 48.0 g | 46.8 g |
| Rust on the exposed steel screws | none | none |
Explain how the results show that the zinc gives sacrificial protection rather than acting only as a barrier.
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.