One classic approach when looking at the conditions necessary for rusting in nails is to place a collection of identical nails in different environments. Line up a rack with four test tubes and place one identical nail in each one. Fill three of the test tubes one-quarter full with the following: deionized water; boiled deionized water and two drops of vegetable oil on the surface to prevent air from entering the water; and a tsp. of salt mixed with deionized water. Add a tsp. of granulated anhydrous calcium chloride to the fourth test tube and place a rubber bung in the top to prevent water or air from getting in. Read about what is required for corrosion of nails --- oxygen and water --- before hypothesizing about what will happen to each nail over the coming days. Observe your nails at least once a day before finishing your experiment after no less than three days.
To complete this project you will require three identical glass beakers for each type of nail used. If you use copper, stainless steel, steel, iron, aluminum and zinc nails, for example, you require 18 beakers. In this experiment, there are three different conditions: control, with nothing but the nail in the beaker; one-half filled with regular tap water; and one-half filled with a tbsp. of salt dissolved in tap water. Set up your beakers as such and label them clearly so you know which type of nail is within the beaker and the conditions it is being exposed to. Observe the nails once a day for at least five days, witnessing the differences in the types of nail and the effect that control, water and salt water conditions have on different nails before determining which nails are least and most resistant to corrosion.
Get creative during this science experiment, as you investigate what you can do to iron nails to prevent --- or slow down --- the rusting process. Place four identical glass beakers next to one another and add an iron nail to each one. Then add four substances of your choosing to the beakers, ensuring you completely submerge the nail. You could, for example, coat nails in nail polish, oil or paint --- always read the label before handling paint and make sure to pour your paint in a well-ventilated area. Observe the changes in your nails once a day for at least three days to see if the substances you added were successful in slowing or preventing corrosion. Leave one nail uncovered in a beaker as a control so you can compare it to the submerged nails.
Health and safety should be the overarching concern when conducting science experiments on rust, particularly if you are assisting or supervising children with a science project. Nails can often be sharp, while rust is associated with undesirable health consequences and can stain clothes. You should always wear tough rubber gloves, safety goggles and a protective overcoat or laboratory coat to protect your skin and clothes from nails. Most rusting projects involve reacting nails with different substances, which may be potentially hazardous. Make sure you are completely aware of the characteristics of a substance and any potential reactions with the nails used in the experiment before you start your project.