Explain the process of rusting.

Rusting is a slow process of oxidation of iron exposed to oxygen and water vapour. Both oxygen and water is required for rusting. In absence of either of the latter factors, rusting doesnot occur. The reddish brown substance formed is called rust, having a molecular formula of Fe2O3·xH2O. Here x stands for the number of molecules of water attached to each molecule of ferric oxide. The reactions stand as:- The key reaction is the reduction of oxygen: O2 + 4 â??eâ?? + 2 â??H2O â?? 4 â??OHâ?? Because it forms hydroxide ions, this process is strongly affected by the presence of acid. Indeed, the corrosion of most metals by oxygen is accelerated at low pH. Providing the electrons for the above reaction is the oxidation of iron that may be described as follows: Fe â?? Fe2+ + 2 â??eâ?? The following redox reaction also occurs in the presence of water and is crucial to the formation of rust: 4 Fe2+ + O2 â?? 4 Fe3+ + 2 O2â?? In addition, the following multistep acidâ??base reactions affect the course of rust formation: Fe2+ + 2 â??H2O â?? Fe(OH)2 + 2 â??H+ Fe3+ + 3 â??H2O â?? Fe(OH)3 + 3 â??H+ as do the following dehydration equilibria: Fe(OH)2 â?? FeO + â??H2O Fe(OH)3 â?? FeO(OH) + â??H2O 2 FeO(OH) â?? Fe2O3 + â??H2O read less

RUST A red or brown oxide coating on iron or steel caused by the action of oxygen and moisture. The Rust Process Rust is the process of iron (molecules) oxidizing into iron oxide, or rust. Rust is the common name for a very common compound, iron oxide. Iron (or steel) rusting is an example of corrosion, an electrochemical process involving an anode, an electrolyte and a cathode . When metal corrodes, the electrolyte helps provide oxygen to the anode. As oxygen combines with the metal, electrons are liberated. When they flow through the electrolyte to the cathode, the metal of the anode disappears, swept away by the electrical flow or converted into rust. For iron to tranform into iron oxide, three things are needed: iron, water and oxygen. When water droplets are gathered on an iron object, two things immediately happen. First, the water combines with carbon dioxide forms a weak carbonic acid, becoming better electrolyte. As the acid is formed and the iron dissolved, some of the water will begin to break down into its component pieces -- hydrogen and oxygen. The free oxygen and dissolved iron bond into iron oxide, in the process freeing electrons. The electrons liberated from the anode portion of the iron flow to the cathode, which may be a piece of a metal less electrically reactive than iron, or another point on the piece of iron itself. The oxidation needs a transfer medium to occur, such as water. Salt in the water speeds up the oxidation process by acting as a catalyst. The problem with salt is that once the water is gone; the salt lies in wait to restart the forming of rust once more moisture is present. read less