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Principle of corrosion-resistant galvanized sheet

Principle of corrosion-resistant galvanized sheet
1, the basic principles of corrosion
Definition of metal corrosion of metal and their physical and chemical environment, leading to changing metal properties and function environment often makes metal product or production process system has been damaged. Metal corrosion, including chemical corrosion and electrochemical corrosion.
A chemical attack
Occurrence of metal and the surrounding medium caused by direct chemical reaction of damage, no current generation. It occurs in a dry atmosphere or in an anhydrous organic liquid. Including high temperature oxidation, high temperature curing, high temperature carburizing, decarbonization, high temperature hydrogen corrosion.
B electrochemical corrosion
Electrochemical corrosion of metal in a wet environment through corrosion of the electrode reaction is carried out, this process an electron gains and losses and generate a current. Most metals, in the vast majority of the natural environment are of corrosion electrochemical corrosion.
2, the corrosion-resistant galvanized steel
In neutral or slightly acidic (PH> 5.2) atmospheres galvanized steel corrosion product layer was formed by etching a non-soluble compound (zinc hydroxide, zinc oxide and zinc carbonate), these products will be precipitated in the form of precipitation, forming a thin layer of dense, generally up to 8μm, this film has some thickness is not easy to dissolve in water, and strong adhesion, so it can play the role of isolation barrier atmosphere and galvanized sheet, to prevent further development of corrosion .
The destruction of the protective zinc coating, part of the surface of steel exposed to the atmosphere, then zinc and iron to form micro-battery, the potential of zinc was significantly lower than the potential of iron, zinc is used as an anode to protect the steel substrate sacrificial anode role in preventing steel corrosion. Should the steel surface when exposed to too much, so that the electrolyte can not be damaged surface coverage, then the iron is not subject to any protection if the same will soon be corroded.
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