النتائج (
الإنجليزية) 2:
[نسخ]نسخ!
Eroding the surface of the minerals found in the case of a chemical or Kahrokimaaúa interaction with the outside center, and this is called rust corrosion.
rust and cause heavy losses in the global economy, estimated Balemyarat annually, as destroys a huge amount of metal structures and machinery. And for rust resistance must know its causes and feasible means to resist.
There are two types of rust: - rust chemical and - electrochemical. rust chemical: and is caused by interaction of the metal with dry gas and insulating fluids without the appearance of an electric current. such as the oxidation of the exhaust valves internal combustion engines and exhaust pipes and combustion fireplaces and internal mechanical links rooms in furnaces and engines. rust electrochemical: As a result of the emergence of electric current is created as a result of the interaction between the metal and the electrons surrounding it, such as steel, cast iron and other alloys in the wet air and in fresh and sea water water and acids and alkalis and brines and in the earth. the crystal lattice of the metal from the positively charged ions composed (cations) are present in the crystal lattice of staff and free electrons moving in the whole metal. And can be separated from the surface of the metal cations and moving to the center next door - electrolyte. And called the effort formed at the surface of the metal contact teams with electrolyte and is indicative of the tendency of the metal melting polar effort. And mainly its value depends on the installation of electrolyte. and determines the polar Metals effort experimentally by comparing the hydrogen effort and is what counts equal to zero. and minerals vary effort polar There is a negative voltage and other metals positive Mqarndta magnate pH (electrode). Minerals voltage positive (above zero hydrogen ) usability few steel and metal cathode voltage (below zero hydrogen) are more susceptible to rust whenever its negative. and pure metals and alloys only phase resist rust well. The alloys that structure consists of several phases with different efforts are for electric micro column many tiny electrodes, and so it is easy to rust. And be parts made of several different materials, metallic efforts electrically micro column at a young age becomes low metal effort lifts anode, and eroding, while the metal is not eroded with the effort Top for his role cathode cathode. actually, for example when touching iron with zinc (iron coating zinc ), eroding zinc (ie is happening to him, steel) ie it is the elevator anode while not eroding the iron because the airstrip cathode. In another example of when you touch the tin with iron (iron paint tin), the iron is eroding (ie stainless steel) have elevator anode. The tin Vsubh airstrip and not eroding. and can be positive or negative, the metal for the impact of the center and is determined by positive metal Btaklh in the center of rust Ktakl iron in the middle of oxidizer at high temperatures. In some of the metals, such as aluminum and chrome all get Oxidation layer consists Oxides of working to protect the metal from corrosion continuity.
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