Effect of Sodium Chloride on Rust

Corrosion is the breaking down or destruction of a material, especially a metal, through chemical reactions. the most common form of corrosion is rust which occurs when iron combines with oxygen and water.”(Dictionary.com, 2018) “like pure iron, corrode quickly. Stainless steel, however, which combines iron and other alloys, is slower to corrode and is therefore used more frequently.”(The Balance, 2018)

Oxygen and water need to be present in order for corrosion to occur. “Corrosion happens through a series of reduction-oxidation reactions, similar to those of a battery. The metal being corroded acts as the anode; the metal is oxidized, forming metal ions and free electrons. The free electrons reduce the oxygen, often times forming hydroxide, and providing a complimentary cathodic reaction. The dissolution of the metal at the anode has two possible outcomes; the metal ions can go into solution, becoming hydrated, or the metal ions can form a solid compound that collects on the surface. In the former case, further oxidation of the metal ions can occur and an open pit can form.” (Chemistry LibreTexts, 2018)

In an open environment usually water easily comes in contact with an iron object, there are two possible reactions that start almost instantly. The first one is when the water is mixed with carbon dioxide in the air to create a weak carbon acid. Some of the water starts to separate into its elements, hydrogen and oxygen. While the acid is being formed and the iron is dissolving. Since the process of corrosion is electrochemical in nature, increasing the temperature usually also increases the rate of corrosion. “This is because if you heat a substance, the particles move quicker and so collide more frequently. A major factor in the rate of corrosion is humidity and time-of-wetness.” (clark, 2018) The duration of time a metal is exposed to enough moisture to initiate the corrosion process relates to the time-of-wetness. “Thus, increased humidity and a greater time of wetness increases the rate of corrosion, providing oxygen is present” (Painting, 2018)

During the process of corrosion, water acts as the solvent for the solute oxygen to break down into. Since oxygen can liquefy in water and since there is usually a surplus to it, the oxygen reacts with the iron hydroxide. The factors the we will be investigating is how different kind of sodium chloride concentration (independent variable) can affect iron nails (dependent variable) in compare with water (control) there will be five beakers with one, three, five, ten, thirty percent of sodium chloride along with one beaker with only water which it will be the control. To make this a fair experiment, will be adding the same volume of solution to each beaker. All the beakers will be kept at room temperature. The controlled variables will include the temperature, the amount of solution in each beaker, the size of the beaker, type of beaker, and the type of nail. During the process of corrosion electrons are transported from one substance to another. Electrons produced from the oxidation of iron where iron acts as the anode are transferred to reduce oxygen, forming hydroxide ions. Salt dissolve in the water in which produces sodium and chloride ions and the presence of these charged particles hugely improves the capability of the electrolyte to carry ions and accelerates the rate of corrosion.

The bigger the concentration of sodium chloride, the more ions in solution hence allowing more redox reactions to occur. Electrons move far more easily in salt water due to the presence of ions and because rusting is fundamentally the movement or transfer of electrons, the presence of these ions allows a quicker rate in the transfer of electrons and so more rapid corrosion. Thereby it can be hypothesized that higher concentrations of sodium chloride will increase the rate of corrosion. It is believed that if the iron nails are placed in a high concentration of sodium chloride would have the highest rate of corrosion which will corrode more quickly than the nails in lower concentrations. This is because the higher concentrations of sodium chloride has more ions that assist in transferring cations and anions through the electrolyte (the solution) which speeds up the corrosion rate of iron, which then involves the transfer of electrons. The electrons produced from the oxidation of iron are transferred to oxygen in reduction.