what is the significance of water or dampness in the formation of rust. chemical equation would help.?
408981
For iron to become iron oxide, three things are required: iron, water and oxygen. Here's what happens when the three get together:\nWhen a drop of water hits an iron object, two things begin to happen almost immediately. First, the water, a good electrolyte, combines with carbon dioxide in the air to form a weak carbonic acid. As the acid is formed the iron dissolves.  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.\nThe chemical compounds found in liquids like acid rain and seawater make them better electrolytes than pure water, thus they speed the process of rusting on iron.
429346
Oxygen is a oxidizer, it oxidizes the apple the same way as oxygen makes steel rust. Almost everything reacts to Oxygen. The browning is caused by enzymes in the fruit reacting to the oxygen in the air. I have included a link below to an experiment with the apple. In reading the experiment, you will find out what effect say sugar has on the browning effect of the apple. The chemical equation posted above, 4 Fe + 3 O2 -----> 2 Fe2O3 is that of rusting iron, not of an oxidized apple.Good Luck with your experiment, you might wish to google the terms "Oxidation + Foods" and do a little more research.
408591
When iron turns to rust, the resulting rust is heavier than the original object.
987656
Simplest example: water, H2O is a liquid, non-flammable, compound made from hydrogen, H2 and oxygen, O2, which are both gasses and very reactive. \n\nAnother: iron, Fe, is a shiny strong metal, while rust FeO2 is a red-brown fragile dust.
555396
try this\n\nhttp://antoine.frostburg.edu/chem/senese/101/inorganic/faq/iron-reactions.shtml
1157885
There are a vast number of water soluble corrosion inhibitors.\n\nAt the simple end of the scale - Sodium nitrite, sodium tolytriazole, zinc phosphate, borates, molybdates, vanadates and chromates all inhibit rust.\n\nThere are also proprietary organic compounds (some phosphate esters, ethanolamides, etc) also inhibit rust.\n\nIt all depends on whether you want the inhibition to be short lived or long lived (nothing is "permanent") and whether the inhibition is an "in use" inhibitor (like, say, a corrosion inhibitor in cooling water) or "static" (like phosphate "rust converters" used prior to painting.
708657
Vinegar is an acid and is also a catalyst for corrosion of iron\n\nOil is hydrophobic and will prevent oxidation from occurring, therefor preserving the iron\n\nWater will promote oxidation and in turn degrade the iron to iron oxide (rust)
462127
Chromium has been added, so it is less likely to rust (thus "stainless")
679627
The more surface area is open to the air, or oxygen, the faster it rusts.  That's why a sheet, which is pretty much totally exposed, will rust fast, but not thick parts like the engine, etc.  Rust, after all, is the product of Iron mixing with Oxygen.  Also, steel is a mixture, more specifically a metal alloy, of iron with carbon.  Alloys with higher carbon content than this are known as cast iron.  Therefore, cast iron rusts slower than sheet metal also because it contains a lot of carbon, rather than being all iron.  I don't know what is better for the garden, but "cast iron" is actually steel, with high amounts of carbon in it.
531919
errrrrrr Oxygen, hence rusting is stricly called oxidisation.  But perhaps you should inform your questioner that Water is actually made up of Hydrogen and Oxygen, therefore some of the answers are obsolete.\n\nThink about the fact that metalwork inside a waterproofed building goes rusty as well as that outside.
972949
WARNING:  Answer is NOT OXYGEN.\n\nIt is true that when metals rust, it forms metal oxides.  But by definition, Catalyst Speeds up the process of the Rxn but does not get used up.  However as you can see in the equation below, Oxygen is consumed with metal to for metal oxide.  Therefore Oxygen CAN'T be a catalyst.  It is a reactant.\n\nFe + O2 ---> Fe2O3\n\nThe Correct answer is SALT.  (Sodium in NaCl for an example)\n  \nRust is the process of metal oxidizing into metal oxide.  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 salt is never used up and the problem with salt is that even when water is gone, it remains and wait to restart the forming of rust once more moisture is present.  This is why metals rust much easily in salty areas such as beaches and cold states where they use salt to melt the icy roads.   \n\nI hope you get my answer in time, if this question if for school.  I know I'm against 3 answers here but let my past records of best answers speak for itself.
237914
biodegrading, or rusting, or rotting
209656
Calcium/ rust buildup. First, you can try ordinary vinegar. Take off the head and soak the piece in vinegar overnight. That may dissolve the calcium. If not, try CLR or similar product, they work wonders!
1030054
You would find, if you had a sensitive enough measuring system, that the energy is dispersed through the acid as heat. \n\nWhen acid oxidises metal there is an initial activation energy required to break the metal lattice and that energy nromally comes from the heat already in the system. When the lattice is under stress sit requires far less energy to break down and the activation energy is lower. That means that more heat is retained by the system as heat.\n\nYou can see for yourself that a metal lattice under stress breaks down and oxidises more readily by simply bending an iron nail and dropping it in a few mm of salt water for a few days. The iron will rust almost exclusively where it was bent. That is because the  bend represents a point of stress in the lattice.\n\nWith less energy required to break down the metal alttice the overall reaction becomes more energetically positive and the amount of heat in the system increases.\n\nThe amount of additional heat this represents is tiny, but with an incredibly stable atmosphere and a very sensitive thermometer you would regeister the lost energy as a higher temperature than an identical beaker of acid with an uncompressed spring.
747628
Aluminium is a chemical element and metal.\nAluminium nails would be nails made of this elements.\n\nCorrosion/rust is the contact of metals with oxygen (another chemical element and part of the air around us), the process is alled oxidation.\n\nThe best example is the metal iron reacting with oxygen from the air  and the result would be rust. (it works better with water as ths contains more of the element oxygen). The surface becomes reddish-brown and briddle, more oxygen can penetrate the metal and in the end the piece of metal breaks, "it rustes away".\n\nAlumumium does react withs oxygen but only on the surfcae, in common language you could say its "rusts". The surface than looks greyish.  But in comparison to iron this forms a protecting layer on the surface of the aluminum, no oxygen can get deeper and the aluminium stays stable.\n\nThat is one of the reason airplanes are made of a very pure aluminium. They should not rust.
1122012
Hmmm... I've never heard that term either.  Is that some sort of microbe that can contribute to the newer problem of Microbiologically Influenced Corrosion?\n\nAre you sure you spelled it correctly?
429906
Never trust materials science majors ...\n\n1. NaCl (s) --> Na+ (aq) + Cl- (aq)\n2. Ca (s) + 2H2O (l) --> Ca(OH)2 (s) + H2 (g)\n3. Ca(OH)2 (s) --> H2O (g) + CaO (s)