How does salt affect the corrosion of iron ?

Question

Identify how salt affects the corrosion of iron and write a short intro concerning what is known about salt and corrosion.

I need it in simple terms, so a kid who knows basically nothing about science can understand. thanks

Answer 1

corrosion is an action of acids
salts being neutral act against corrosion
they slow down the process of corrosion

Answer 2

Salt Water Corrosion

Answer 3

Corrosion rate:
Sodium chloride : 41-46 mils/year .

For corrosion to occur, four elements must be in place. These are:

Two dissimilar metals.
A connection between the two metals.
An electrolyte, such as water.
A potential difference between the two metals.
The salt does 3 things:
1. attract water (thus speeding corrosion)
2. makes water a better conductor (thus speeding corrosion).
3. break down into chemicals that bind to the metal atoms, oxidizing them (thus speeding corrosion)

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Salts are not acidic, as the first poster says, but they do produce ions, which are electrolytes. Electrolytes allow a current of electricity to pass through the solution of the salt. This allows electrolytic reactions to take place, causing the metals to be oxidized and become metals cations. The metal cations dissolve in the solution and contribute to a increase in the electrical current that is being generated.
(Salt can affect rate of corrosion even if there is no water present. This is due to the following reasons:

NaCl dissolves into Na+ and Cl- ions in the presence of water. These ions act as conductors of electricity and make the water more conductive. This increases the rate of corrosion.

Cl- ion is a strong reducing agent. Therefore, it attacks the iron (III) oxide layer already formed and exposes a new layer of iron. This also speeds up the rate of reaction.

Finally, even if there is no water, NaCl itself has the property of hydroscopicity. That means that it has the ability to absorb water even from the atmosphere.

All these factors sum up to make salt a major contributor to corrosion. )
Yes, it’s true that salt water carries with it increased rates of galvanic corrosion over fresh water, however, galvanic corrosion itself is not just limited to the saltwater environment. Galvanic corrosion can occur outside on a humid day!

The more active the metal, the more corrosion will take place when the above mentioned situation is present. All metals range from very active, such as Magnesium and Zinc, to the least active, such as Gold and Stainless Steel. Drive units and engine parts could be made of stainless steel, however, the cost would be enormous, and the weight would be unacceptable.

http://www.screamandfly.com/home/engine_tech/galvanic_corrosion/galvanic_corrosion.htm

Answer 4

The chlorides are extremely corrosive to all steels, not just iron, stainless too. The ions in salt, mainly chloride, create galvanic cells oxidizing the metal. The metal ions will leave the steel, flaking off. Sea water is a major source of corrosion, also water entrained in crude oils cause major problems in refineries. Salt deposition (ammonium chlorides/sulfies) will lay down in 'clumps' in pipes causing the velocity to increase, resulting in a form of erosion corrosion which is mechanical form of corrosion, there's lot's of forms of corrosion. Salt is a major culprit, and there is a lot of research into this subject - try NACE for more info.

Answer 5

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How does salt affect the corrosion of iron ?
Identify how salt affects the corrosion of iron and write a short intro concerning what is known about salt and corrosion.

I need it in simple terms, so a kid who knows basically nothing about science can understand. thanks

Answer 6

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I guess this should really be in the Chemistry section rather than the Physics section... however: The corrosion of iron is an electrochemical process. The iron is oxidised by whatever oxidants are present in the environment. Oxygen and chlorine are very effective oxidants. Thus you would expect an aerated solution of sodium chloride to be a more effective oxidant than distilled water with little or no dissolved oxygen. The water itself has little effect except to act as a transport medium for the various reactions.

Answer 7

Rust is oxidation of iron when exposed to water. The water gives electrons to cause oxidation to occur.

The presence of a salt greatly enhances rusting. The dissolved salt is made of Na+ and Cl-, which increases the conductivity of the water on the metal and enhances the rate of electrochemical corrosion.

Answer 8

Salt and iron is a special case. The main reason why salt can corrode iron so easily is because when iron gets rusty due to salt it falls off and exposes more of the metal which corrodes and falls off and so on.

Answer 9

the sodium in the salt creates wird chemical reactions when it contacts the iron