why is painting in metal prevent corosion?
110798
Corrosion is caused by oxidation. By painting the metal, you add a barrier to protect the metal from direct exposure to the air, which contains oxygen.
716754
it prevents the steel from rusting. Zinc rusts too, but more slowly than steel, and it doesn't tend to eat away it's structure. \nZinc coatings prevent oxidation of the protected metal by forming a barrier, and by acting as a sacrificial anode if this barrier is damaged. Zinc oxide is a fine white dust that (in contrast to iron oxide) does not cause a breakdown of the substrate's surface integrity as it is formed. Indeed the zinc oxide, if undisturbed, can act as a barrier to further oxidation, in a way similar to the protection afforded to aluminium and stainless steels by their oxide layers.
696386
well it depends on the metal the bin is made of. If its made of a metal below Zn in the electrochemical series, then the Zn is oxidised (rusts) in preference to the metal the bin is made of. This is known a sacrificial protection, as the layer of Zn is 'sacrificed'
433170
The company I work for does Salt Spray Analysis. it's used to find out how well a coating holds up under controlled conditions. Salt water is very corrosive to most metals and is a good medium for testing for corrosion.\n\nBasically, a part that has a coating (paint, Anodize, Nitride, Black Oxide,...) is placed in a sealed tank. The tank sprays water with a particuar amount of salt in it into the chamber. The parts are checked every hour, 2 hours, 6 hours...as directed by the requirements. As soon as ANY rust is found, the testing stops and the amount of time it took for the rust to show is recorded. 300 hours is very good for any type of paint.
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.
147407
Rusting is a chemical process that, can take place in metals exposed to the atmosphere. Not all metals however rust. Rusting is common with the metal, iron. Certain conditions in the air around a metal have to be present for iron to rust. Iron rust which, generally appears brown, is itself a chemical compound quite different from the iron itself. The rusting of iron can be prevented. In towns and large cities where iron sheets are used for roofing houses, rusting can also take place if the iron sheets are not protected from rusting. \n\nRust is the common name for a very common compound, iron oxide. Iron oxide, the chemical Fe2O3, is common because iron combines very readily with oxygen -- so readily, in fact, that pure iron is only rarely found in nature. Iron (or steel) rusting is an example of corrosion -- an electrochemical process involving an anode (a piece of metal that readily gives up electrons), an electrolyte (a liquid that helps electrons move) and a cathode (a piece of metal that readily accepts electrons). When a piece of 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 metal cations in a form such as rust.\n\nFor iron to become iron oxide, three things are required: iron, water and oxygen. Here's what happens when the three get together:\n\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, an even 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.\n\nThe chemical compounds found in liquids like acid rain, seawater and the salt-loaded spray from snow-belt roads make them better electrolytes than pure water, allowing their presence to speed the process of rusting on iron and other forms of corrosion on other metals.
31275
brass actually oxidizes because of the exposure to oxygen.\n\nOxidation is the interaction between oxygen molecules and all the different substances they may contact, from metal to living tissue. Sometimes oxidation is not such a bad thing, as in the formation of super-durable anodized aluminum. Other times oxidation can be destructive, such as the rusting of an automobile or the spoiling of fresh fruit.\n\nWe often used the words 'oxidation' and 'rust' interchangeably, but not all materials which interact with oxygen molecules actually disintegrate into rust. In the case of iron, the oxygen creates a slow burning process, which results in the brittle brown substance we call rust. When oxidation occurs in copper, on the other hand, the result is a greenish coating called copper oxide. The metal itself is not weakened by oxidation, but the surface develops a patina after years of exposure to air and water.\n\nThe process of oxidation depends on the amount of oxygen present in the air and the nature of the material it touches. True oxidation happens on a molecular level -- we only see the large-scale effects as the oxygen causes free radicals on the surface to break away. In the case of fresh fruit, the skin usually provides a barrier against oxidation. This is why most fruits and vegetables arrive in good condition at the grocery store. Once the skin has been broken, however, the individual cells come in direct contact with air and the oxygen molecules start burning them. The result is a form of rust we see as brownish spots or blemishes.
444530
in the periodic table that has the symbol Sn (L. Stannum) and atomic number 50. This silvery, malleable poor metal that is not easily oxidized in air and resists corrosion is found in many alloys and is used to coat other metals to prevent corrosion. Tin is obtained chiefly from the mineral cassiterite, where it occurs as an oxide.\nNotable characteristics\n\nTin is a malleable, ductile, highly crystalline, silvery-white metal whose crystal structure causes a strange crackling sound known as the "tin cry" when a bar of tin is bent (caused by crystals breaking). This metal resists corrosion from distilled, sea and soft tap water, but can be attacked by strong acids, alkalis, and by acid salts. Tin acts as a catalyst when oxygen is in solution and helps accelerate chemical attack.\n\nTin forms the dioxide SnO2 when it is heated in the presence of air. SnO2, in turn, is feebly acidic and forms stannate (SnO3-2) salts with basic oxides. Tin can be highly polished and is used as a protective coat for other metals in order to prevent corrosion or other chemical action. This metal combines directly with chlorine and oxygen and displaces hydrogen from dilute acids. Tin is malleable at ordinary temperatures but is brittle when it is heated.\n\n\nAllotropes\n\nSolid tin has two allotropes at normal pressure. At low temperatures it exists as gray or alpha tin, which has a cubic crystal structure similar to silicon and germanium. When warmed above 13.2 °C it changes into white or beta tin, which is metallic and has a tetragonal structure. It slowly changes back to the gray form when cooled, which is called the tin pest or tin disease. However, this transformation is affected by impurities such as aluminium and zinc and can be prevented from occurring through the addition of antimony or bismuth.\n\n\nApplications\n\nTin bonds readily to iron, and has been used for coating lead or zinc and steel to prevent corrosion. Tin-plated steel containers are widely used for food preservation, and this forms a large part of the market for metallic tin. Speakers of British English call them "tins"; Americans call them "cans". One thus-derived use of the slang term "tinnie" or "tinny" means "can of beer". The tin whistle is so called because it was first mass-produced in tin-plated steel.\n\nOther uses:\n\n    * Some important tin alloys are: bronze, bell metal, Babbitt metal, die casting alloy, pewter, phosphor bronze, soft solder, and White metal.\n    * The most important salt formed is tin chloride, which has found use as a reducing agent and as a mordant in the calico printing process. Electrically conductive coatings are produced when tin salts are sprayed onto glass. These coatings have been used in panel lighting and in the production of frost-free windshields.\n    * Window glass is most often made via floating molten glass on top of molten tin (creating float glass) in order to make a flat surface (this is called the "Pilkington process").\n    * Tin is one of the two basic elements used since the Rennaisance in the manufacture of organ pipes (the other being lead). The amount of tin in the pipe defines the pipe's tone, tin being the most tonally resonant of all metals.\n    * Tin is also used in solders for joining pipes or electric circuits, in bearing alloys, in glass-making, and in a wide range of tin chemical applications. Although of higher melting point than a lead-tin alloy, the use of pure tin or tin alloyed with other metals in these applications is rapidly supplanting the use of the previously common lead–containing alloys in order to eliminate the problems of toxicity caused by lead.\n    * Tin foil was once a common wrapping material for foods and drugs; now replaced by the use of aluminium foil, which is commonly referred to as tin foil. Hence one use of the slang term "tinnie" or "tinny" for a small retail package of a drug such as c
236628
Corrosion occurs when a material is exposed to oxygen (oxidation). The best way to avoid oxidation is by protecting the material from coming in touch with the oxygen by painting over it or sealing it in any other way.
112405
It is evidently the chrome, etc. covering of plastic parts to make them gleam bright.  It may start with non-electrolytic coating(s) that can then be electroplated.
250184
While the corroded part of the copper shield will have altered conductivity, there still is a metal surface - the border to the patina - where metal conductivity occurs. There might be a slight increase in resistivity, but not significant compared to contact corrosion.
672632
i don't know exactly how it works but rust is caused by oxidisation, which is a reaction between oxygen and the metal. i'm not sure why, but water speeds up the process, allowing the oxygen in. but water does not cause rust. oxygen does.
796939
Process Issue.\n\nThe Metal prior to Plating must be free of all contaminants.\n\nHave the Process and quality staff examine the Brass prior to the Plating and do a Controlled experiment with a sample size run.\n\nPerhaps a contaminate is entering the Process at a stage in the Handling of the Brass.\n\nProcess control must be verifiable at all times.\n\nClosing down the Line is costly and very expensive. But, The Product that the customer receives must be defect free.\n\nPlease review the following URL:\n\nhttp://www.finishing.com/96/76.shtml\n\nContact me by email, if I can offer addition assistance.\n\n\nRegards.
213711
Obviously, an unreactive metal. Well, you can galvanise the zinc, or you can paint it (I'm serious).
244814
Yes, it does.  This is because the salt provides electrolytes and allows for faster oxidation.  Salt water spray is often the test method used to determine if a given paint offers more corrosion protection than a standard reference paint.  Corrosion inhibitors, like zinc chromate and others, offer protection by  interfering with the oxidation process.
118571
corrosion is actually oxidation. A chemical reaction between oxygen and various materials such as metal. Painting metal prevents oxygen from reaching the metal and stops the chemical reaction.
1176918
a chromate coating applied to metals to make the surfaces corrosion resistant. (prevent rust)