Why does the same material behave differently once it has been treated, coated or finished, and how do you test for that change?
How treatments, coatings and finishes change the performance of materials, how stock forms and standard components are supplied, and how materials are tested for strength, hardness and durability.
A focused answer to AQA A-Level Design and Technology Product Design 3.1.2, covering treatments, coatings and finishes, stock forms and standard components, and the standard tests used to measure material performance.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
AQA wants you to explain how treatments, coatings and finishes improve the performance and appearance of materials, recognise the stock forms and standard components materials are supplied in, and describe the standard tests used to measure properties such as strength, hardness and durability.
Treatments
Treatments are usually done before finishing and can make a cheaper base material perform like a more expensive one. The key examples to know precisely are the heat treatments of steel. Hardening heats steel and quenches it rapidly to make it very hard but also brittle; tempering then reheats it gently to trade a little hardness back for much greater toughness, so a tool is hard enough to keep an edge without shattering. Annealing is the opposite, softening a metal by slow cooling so it can be worked more easily. Case hardening hardens only the outer skin of a low-carbon steel, giving a wear-resistant surface over a tough core. Work hardening occurs when a metal is cold-worked (bent or hammered), making it harder but more brittle, which is why repeatedly bending a paperclip eventually snaps it. Seasoning of timber removes moisture so it is stable and less likely to warp or rot. These change the material itself, which is what distinguishes them from finishes applied on top.
Coatings and finishes
Finishes protect against corrosion, wear and moisture, and improve appearance.
- Metals: painting, powder coating, anodising aluminium, galvanising steel with zinc, electroplating.
- Timbers: varnish, oil, wax, paint and stain to resist moisture and wear.
- Polymers: usually self-finishing, so they need little surface treatment.
Stock forms and standard components
Testing materials
Designers use standard, often destructive, tests so results can be compared against published data.
- Tensile test: pulls a sample until it breaks to find tensile strength and ductility.
- Hardness test: presses an indenter into the surface (Brinell, Vickers).
- Toughness or impact test: strikes a notched sample (Izod, Charpy).
- Fatigue test: applies repeated loading cycles to find the life of a part.
Knowing which test measures which property earns marks: a tensile test gives strength and ductility, a hardness test gives resistance to indentation, an impact test gives toughness, and a fatigue test gives resistance to repeated loading. Because the tensile, impact and fatigue tests destroy the specimen, manufacturers test a representative sample from a batch rather than every part, and compare the result against published standard values so materials from different suppliers can be judged on the same basis. This links testing to quality control and to the standards topic: a consistent, tested material is the foundation of a product that reliably meets its specification.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20196 marksA steel garden bench will be used outdoors. Explain how treatments and finishes could be used to improve its performance and appearance, and explain why a manufacturer tests the steel before production. [6 marks]Show worked answer →
A Paper 1 extended item assessing applied knowledge. Markers reward treatments and finishes correctly distinguished plus a reason for testing. Award marks for: a treatment changes the internal or surface structure (for example hardening and tempering to balance hardness with toughness), while a finish is applied to the surface; for outdoor steel, galvanising (a zinc coating) or powder coating resists corrosion and weather, and also improves appearance. Award marks for testing: standard, often destructive, tests (tensile for strength and ductility, hardness, impact for toughness) on a representative sample confirm the steel meets the specification and is consistent batch to batch, so failures are caught before production. A top answer notes that testing a sample, not every part, is necessary because the tensile test destroys the specimen.
AQA 20214 marksExplain why manufacturers use standard stock forms and standard components, giving an example of each. [4 marks]Show worked answer →
A short-answer item. Award marks for: standard stock forms are materials supplied in consistent off-the-shelf sizes (sheet, bar, rod, tube, extrusion, granules), which are cheaper, readily available and reduce waste and machining (example: standard steel tube for a frame); standard components are mass-produced bought-in parts made to a consistent specification (screws, bolts, bearings, hinges), which are cheaper than making your own, reliable, interchangeable and speed up assembly (example: a standard ball bearing). Full marks need a benefit (cost, availability, consistency or speed) plus a valid example for both stock forms and components.
Related dot points
- The classification of materials into papers and boards, timbers, metals, polymers, composites and technical textiles, and the physical and mechanical properties that decide which material suits a given application.
A focused answer to AQA A-Level Design and Technology Product Design 3.1.1, covering how materials are classified into the main families and the physical and mechanical properties used to select a material for a product.
- The main shaping, forming, casting, moulding and joining processes for the material families, and how scale of production (one-off, batch, mass and continuous) drives the choice of process, tooling and cost.
A focused answer to AQA A-Level Design and Technology Product Design 3.1.3, covering the main manufacturing processes for each material family and how the scale of production drives the choice of process, tooling and cost.
- Modern materials developed through invention or improved processing, and smart materials that change a property in response to an external stimulus, including shape-memory alloys, thermochromic and photochromic materials, piezoelectric materials and electroluminescent wire.
A focused answer to AQA A-Level Design and Technology Product Design 3.1.4, covering modern materials and smart materials that change a property in response to a stimulus, including shape-memory alloys, thermochromics, piezoelectrics and electroluminescent wire.
- Health and safety in design and manufacture, the role of risk assessment and legislation, and the standards and safety marks such as the British Standards Institution Kitemark, the CE and UKCA marks and ISO standards that products must meet.
A focused answer to AQA A-Level Design and Technology Product Design core content, covering health and safety in design and manufacture, risk assessment and legislation, and standards and safety marks such as the BSI Kitemark, CE, UKCA and ISO.
- Sustainable design and the six Rs, life cycle assessment from raw material extraction to disposal, the impact of manufacturing on the environment, and strategies such as design for disassembly, the circular economy and ethical sourcing.
A focused answer to AQA A-Level Design and Technology Product Design core content, covering sustainable design, the six Rs, life cycle assessment, the environmental impact of manufacturing, and strategies such as design for disassembly and the circular economy.