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Theory What is rust? Rust is the common name of a compound, iron oxide. Iron oxide, the chemical Effie, 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).
Causes 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 actions in a form such as rust. For iron to become Iron oxide, three things are required: Iron, water and oxygen. Here’s what happens when the three get together: When 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 o 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, Consequences Rusting has a number of effects on metal objects.
It makes them look orange and rough.
It makes them weaker, by replacing the strong Iron or steel with flaky powder. Some oxides on some metals such as aluminum form Just a thin layer on top which lows down further corrosion, but rust can slowly eat away at even the biggest piece of iron. If a piece of Iron’s strength Is important for safety, such as a bridge support or a car’s brake caliper. It Is a good Idea to Inspect It for rust damage every now and then. Rust also can cause metal parts that are supposed to slide over one another to become stuck.
Rust can make holes In sheet metal. Rusty car mufflers sometimes develop holes in them, and the sheet steel making the outer bodies of cars will often rust through, making holes. Rust Is a lot less magnetic than Iron. An iron magnet will probably still work almost as ell when It has a thin coating of rust on It, but If It has rusted so badly that most of the metal is gone, then it will not work very well as a magnet. 1 OFF which is a metallic conductor.
So if some electrical connection is made with iron, it’s likely to go bad when the iron surface rusts. Rust is associated with degradation of iron-based tools and structures. As rust has a much higher volume than the originating mass of iron, its build-up can also cause failure by forcing apart adjacent parts ? a phenomenon sometimes known as “rust packing”. It was the cause of the collapse of the Missus river bridge in 1983, when he bearings rusted internally and pushed one corner of the road slab off its support.
Rust was also an important factor in the Silver Bridge disaster of 1967 in West Virginia, when a steel suspension bridge collapsed in less than a minute, killing 46 drivers and passengers on the bridge at the time. Prevention and Protection Because of the widespread use and importance of iron and steel products, the prevention or slowing of rust is the basis of major economic activities in a number of specialized technologies. A brief overview of methods is presented here; for detailed overage, see the cross-referenced articles.
Rust is permeable to air and water, therefore the interior metallic iron beneath a rust layer continues to corrode. Rust prevention thus requires coatings that preclude rust formation. Some methods of prevention of rusting are as follows: Gallivanting:- Globalization consists of an application on the object to be protected of a layer of metallic zinc by either hot-dip gallivanting or electroplating. Zinc is traditionally used because it is cheap, adheres well to steel, and provides catholic protection to the steel surface in case of damage of the zinc layer.
In more corrosive environments (such as salt water), cadmium plating is preferred. Coating and Painting:- Rust formation can be controlled with coatings, such as paint, lacquer, or varnish that isolate the iron from the environment. Large structures with enclosed box sections, such as ships and modern automobiles, often have a wax-based product (technically a “slashing oil”) injected into these sections. Such treatments usually also contain rust inhibitors. Covering steel with concrete can provide some protection to steel because of the alkaline pH environment at the steel-concrete interface.
Humidity Control:- Rust can be avoided by controlling the moisture in the atmosphere. An example of this is the use of silica gel packets to control humidity in equipment shipped by sea. Metal Coupling:-Len this method, the iron is coupled with other metal and if the metal is above iron in electrochemical series(meaner more electrostatics)then in the galvanic cell is formed by the contact of the iron and that metal, iron will go under reduction it will be safe from rusting. If the metal is below iron in electrochemical series then iron will go under oxidation and rusting will be facilitated.
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