Rusting and Prevention

Place identical steel nails into different household liquids and record changes over several days to compare rusting rates. The activity highlights how oxygen, water, acidity, salt, and barriers like oil affect iron oxidation.

1. Gather 6 clean steel nails, avoiding galvanized nails, and 6 labeled test tubes or clear cups.
2. Prepare separate cups with water, saltwater, vinegar, lemon juice, cola, and cooking oil. Make enough liquid to fully cover a nail where required.
3. Dry and photograph each nail, then record initial observations. Optional: measure and record each nail’s mass.
4. Place one nail into each cup. For the oil condition, first add water to cover the nail, then carefully pour a thin oil layer on top to block air contact. For a half-submerged condition, position a nail so part is above the waterline.
5. Leave all setups at the same location and temperature. Do not move them except to observe.
6. Observe daily at the same time. Note color changes, surface texture, any blackening, bubbling, or deposit formation. Take photos for a time series.
7. Continue for several days until clear trends appear. Optional: remove, rinse, dry, and reweigh each nail to estimate mass change.
8. Compare which liquids produced visible rust first and which slowed or prevented rust. Relate outcomes to oxygen availability, pH, salt content, and barriers.

Rusting of iron | Middle school chemistry | Khan Academy - Khan Academy India - English:

📄 Rusty nail experiment - Fizzics Education: https://www.fizzicseducation.com.au/150-science-experiments/kitchen-chemistry-experiments/rusty-nail-experiment/?srsltid=AfmBOopYP9UICh_szwpHM6m0MMfsmsDgP7q02_JEwHP6ur4trYj5IU9I

• Test different nail types such as bright steel vs stainless vs galvanized, and compare outcomes.
• Use steel wool instead of nails to investigate the effect of larger surface area.
• Compare fully submerged nails vs half-submerged nails to examine the role of air exposure.
• Try different salt concentrations or different acids such as citric solution at measured pH.
• Heat one set gently to investigate temperature effects on reaction rate, keeping all else constant.
• Seal one water sample to reduce air contact and compare with an open sample.

• Adult supervision required when students are involved.
• Wear safety glasses and disposable gloves when handling acids such as vinegar and lemon juice.
• Avoid galvanized nails if acids are used, as coatings can react and release additional ions.
• Do not ingest any liquids. Keep all materials away from food preparation areas.
• Label all containers clearly and keep them on a stable surface to prevent spills.
• Nails have sharp points; handle with care and keep away from young children.
• If heating a sample for a variation, use only lab-approved hot water baths and heat-resistant containers; do not heat sealed containers.

• What is the independent variable in this experiment? (The liquid or condition each nail is placed in.)
• What is the dependent variable? (The extent or rate of rusting, measured by observations or mass change.)
• What are key controlled variables? (Nail size and type, temperature, observation time, liquid volume, and exposure time.)
• Why does saltwater often speed rusting compared with pure water? (Dissolved ions increase solution conductivity, which facilitates redox processes on iron.)
• Why might a nail under an oil layer rust more slowly? (The oil reduces oxygen contact with the water and iron, limiting oxidation.)
• Why can vinegar or lemon juice sometimes turn a nail surface dark instead of orange-brown at first? (Acid removes protective oxides and can form iron acetate or sulfide-like films and magnetite, which can appear black before typical red rust forms in air.)
• Why does a half-submerged nail often rust most at the waterline? (That region has both moisture and abundant oxygen from air, creating optimal conditions for corrosion cells.)
• How would increasing temperature be expected to affect rusting rate? (Higher temperature generally increases reaction rate by providing more kinetic energy for redox processes.)