Eroded surface of the ****l in the case of chemical or electrochemical reaction with the middle and outer, and this is called rust, corrosion.
Rust and cause severe losses in the global economy billions annually, as it destroys a huge amount of ****l structures and machinery. And resistance to rust, you must know the causes and effective ways to resist it. There are two types of rust: chemical and electrochemical corrosion.
Chemical corrosion: It happens because of the ****l interaction with gases, liquids and dry the buffer without the appearance of an electric current.
Oxidants such as exhaust valves of internal combustion engines and exhaust pipes and combustion chambers stoves and internal links in Mechanical furnaces and engines.
Electrochemical corrosion: and arise as a result of the emergence of electricity as a result of the interaction between the ****l and the electrons surrounding it: such as steel, cast iron and other alloys in wet air and in fresh water and sea water and acids and alkalis and salt solutions and in the ground.
Rust: red material, rooted to the color brown, forming on the surface of iron or steel when exposed to moist air, and when you use the term alone, it means the corrosion of iron, which consists mainly of iron oxide and water. It consists of the Federation of rust Ookjsin air with iron in a process known as oxidation.
And can remove a thin layer of corrosion of iron or steel Bgha, or by using a polishing powder, and the thick layers of rust, require the use of coolant to remove them, also used acid to remove rust.
And of indirect causes to be rust bacteria in soil, and which convert salt and acid to sulfuric acid that attacks the iron and cause the rust. Where the eroded concrete result of the chemical reaction that occurs between the sulfur Dissolved (Soluble Sulphates) with cement, leading to poor durability and thus to cracking and fragmentation of its parts.
It is known that alkaline concrete work to put a layer on the rebar protect iron from rust formation of a dense layer alkaline prevent rust (Layer Protection negative). And occurs as a result of corrosion cracking layer passive protection by preventing the access of chloride salts and salts harmful to the concrete reinforcing steel and the intervention of these salts to the body of concrete by external factors such as:
* The surrounding soil with concrete.
* Dust-laden winds that contains salts.
* Spray water saturated with salts in the buildings near the sea or the materials used in concrete mix, such as sand, gravel and water containing a high percentage of salts.
There are several factors that lead to break this class are:
1) carbonation Carbonation: from the air surrounding concrete.
2) attack Alkloraydat Concrete (from the soil surrounding the concrete and materials used Mixed Concrete and non-use of water suitable for mixing).
The entry of other salts to the pores of the concrete materialization inside and cause the disintegration of the outer parts of the concrete gradually "This problem is in the concrete near salt water and sand saturated with salts.
And vary the degree of the impact of these factors on the permeability of concrete with varying concrete where all increased the impact of increased permeability of the above factors.
Corrosion rate is linked to many factors, and are moisture and temperature are key factors and moving very much in the rates of corrosion and therefore must control these factors to prevent a problem of access to technical and economic entity on the concrete ..
Terms of occurrence of corrosion of iron:
Terms of a steel component and the presence of oxygen, water and electrolyte solution.
The process of electrochemical corrosion process occurs when the interface element.
Occurs corrosion of iron as a result of ionization of iron in the water given ions of iron and then reduced to electrons resulting from ionization of iron in the water of dissolved oxygen in the water at the surface of the iron ions are hydroxyl and then combine ions of iron with hydroxyl ions and consists hydroxide iron and in the presence of oxygen, water is oxidized hydroxide, iron hydroxide iron.
Iron and steel consists of a mixture of iron hydroxide, iron hydroxide, and it could be argued that the corrosion of iron occurs if there is both requirements:
1) water or moisture
2) air (oxygen)
In the absence of rust, one of them does not occur (water isolated from the air or free of dissolved air and oxygen or air dry).
Ways to protect ****ls from corrosion:
Used in the industry are different ways to protect and manufactures steel structures such as bridges and skyscrapers and Taking of ships and others, according to the causes of corrosion and rust Zerogah. Can be divided and all the roads in corrosion resistance to the following groups:
And prevention of ****l corrosion by adding elements Spekip
Prevention, treatment of the middle and outer
Prevention mineral paint
When cathodic protection
Prevention coverage of non-****llic
Prevention ****l condom