Introduction
Rust is the common name used to describe a very common compound “iron oxide” which is a product of iron and oxygen as they combine readily to form the chemical Fe2O3, and therefore, it is very hard to find a pure iron in nature. In fact, iron or steel rusting is an excellent example of corrosion whereby an electrochemical processes which involves an anode and an electrolyte (a liquid that helps the electrons move) and a cathode. As oxygen mixes with the metal, electrons are realized, which then flow through the electrolyte to the cathode, with the metal of the anode disappearing as they are converted into metal cations which are deposited in the other rod in form of a rust. 
As such for iron oxide to be formed three ingredients are necessary: iron, oxygen, and water; when some water mixes with an iron object, immediately two things happen, water, a suitable electrolyte, combines with the carbon dioxide in the air to form a weak carbonic acid. The acid so formed dissolves the iron, with some water beginning to break down to its constituents elements- hydrogen and oxygen, then the free oxygen dissolve the iron bond into oxide, releasing electrons in the process which are then deposited on the cathode. Therefore, liquids like acid rain and seawater make perfect electrolytes than pure water, as they contain ingredients which help to speed up the process of rusting on iron (Wang, Gmitter & Sadoway, 2011).
Hypothesis
Iron rusting is one of the problems that has troubled human race for a long time and as such it will be prudent to answer the following question; does iron rust faster in the air, fresh water, salt water or in an acidic or basic environment? And how long will the iron take to rust under the different ph levels, and which is the ph level that is more corrosive to the iron? My hypothesis is that iron will rust faster in the salt water than in fresh water and air; also, I think it will take three days for iron to rust at different environments under various influences.
Materials and Methodology
Experimental methodology and materials needed
Aim:
To investigate where corrosion occurs faster, in water or air?
Materials:
- Four nails
- Four test tubes
- One test tube rack
- Deionized water
- Sodium Chloride ( table salt)
- Boiled deionized water (15-minute boil)
- Cotton wool
- Pens or other means of labeling test tubes
- Calcium chloride
- Oil
Procedure
- Label the test tubes 1-4
- About a quarter, fill tube 1 with deionised water and add a nail
- About a quarter fill tube 2, with boiled deionized water and add a nail, then carefully pour a little oil over the surface to prevent air from reaching the water
- Mix some salt with some deionized water to make a solution and then take a quarter of the mixture to fill tube 3 and add a nail
- Put a nail in tube 4 and add about 2 cm depth of anhydrous calcium chloride granules to absorb water and then cork this tube to prevent any further water from getting in
- Leave the experiment for at least three days and then note the changes in the appearance of the nails. Following is a diagram illustrating the setup of the experiment in a test-tube rack
Experimental Design
Independent variables of this experiment will be the deionized water, boiled deionized water, salty water and calcium chloride because these variables are changing and therefore each has its reaction rate. As such the dependent variable will be the iron nails which are supposed to change when they are subjected to different environments such as being put in salty water and boiled deionized water. The extent to which they will change in the different environments is what will help us to determine which variable speeds up the rusting process in the iron (Wang, Wang & Ke, 2010).
Fixed variable or the control variable in the experiment is the amount of time the experiment will take which will be approximately three days and also; the amount of water and temperature in the test is constant and can also, be categorized in this area as they have a big influence on the final results. The control groups in the experiment are the various independent variables used to test the rate of rusting of the iron nails which are placed in the same environment so that they will not have an impact on the results of the experiment. The experimental group, on the other hand, involves the entire environment in which the experiment will be conducted and the procedures involved in the experiment itself will have an impact on the whole process (Tsai,Sah & Kao,2010).
Methods of Data Collection and Units Used
Observation is the best method that I will use to compare the extent to which different variables will have on the nail as the degree of rusting can be easily observed and the appropriate conclusion being made. Another tool or method appropriate is the use of ph to measure the acidity or basicity of the variable used and which will help to deduce how different ph levels speeds or slows the rusting process
References
Tsai, T. T., Sah, J., & Kao, C. M. (2010). Application of iron electrode corrosion enhanced electrokinetic-Fenton oxidation to remediate diesel contaminated soils: a laboratory feasibility study. Journal of hydrology,380(1), 4-13.
Wang, J., Wang, Z. Y., & Ke, W. (2010). Corrosion behavior of weathering steel in diluted Qinghai salt lake water in a laboratory accelerated test that involved cyclic wet/dry conditions. Materials Chemistry and Physics, 124(2), 952-958.
Pérez, F. R., Barrero, C. A., & García, K. E. (2010). Factors affecting the amount of corroded iron converted into adherent rust in steels submitted to immersion tests. Corrosion Science, 52(8), 2582-2591.
Wang, D., Gmitter, A. J., & Sadoway, D. R. (2011). Production of oxygen gas and liquid metal by electrochemical decomposition of molten iron oxide.Journal of the Electrochemical Society, 158(6), E51-E54.