Steel brackets will be used to support ventilation ducts on a roof. The brackets will be exposed to air and rain. Their coating is likely to be scratched during installation, and the brackets will be difficult to inspect afterwards.
A company scratched each coating to expose the steel and then tested the coated brackets for 12 weeks.
| Coating | Cost of coating one bracket in £ | Area of steel covered by rust after 12 weeks in cm² |
|---|---|---|
| Paint | 1.40 | 12.0 |
| Zinc | 3.80 | 0.0 |
Use the information in the table and your knowledge of rust prevention to evaluate whether the brackets should be painted or coated with zinc.
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.