Galvanized pipe corrosion principle
Date: 2019-09-11
Galvanized pipe corrosion principle
Galvanized steel pipe is is state of molten metal zinc and iron substrate reaction of alloy layer, so that the substrate and the coating combination of both. On the use of technology in galvanized, Hot dip galvanized firstly do the pickling, in order to remove the steel surface of iron oxide, after pickling, through an aqueous solution of ammonium chloride or zinc chloride or ammonium chloride and chlorinated zinc mixed aqueous solution tank for cleaning, and then into hot-dip plating bath. Hot-dip galvanized with coating uniformity, strong adhesion, long life and other advantages. Therefore, techniques by hot dip galvanized steel substrate and the molten bath through complex physical, chemical reaction, the formation of a corrosion-resistant zinc-alloy layer of compact structure. Therefore, galvanized steel alloy layer and layer of pure zinc, steel base blend make the corrosion resistance ability.
Zinc chemical lively sex is higher than iron, when electrochemical corrosion occurs, the first corrosion is zinc instead of iron, zinc oxide and relatively compact, which can prevent further oxidation. Usually galvanized steel has good corrosion resistance, corrosion of buried metal pipes is divided into two kinds of uniform corrosion and localized corrosion, localized corrosion mostly dominated, the danger is the greatest. Steel corrosion in soil electrochemical dissolution process is mainly due to the formation of corrosion cells resulting pipeline corrosion perforation. Press the corrosion cell anode and cathode spacing size, but also shape the steel into micro-cell corrosion corrosion and macro cell corrosion two categories. Electrochemical corrosion for buried pipeline process, steel corrosion inhibition method from which to start a process. If the pipe wall plus anti-corrosion coating, loop resistance can be increased, reducing the corrosion current; external DC power supply, so that the soil pipe causing negative potential, the formation of cathodic protection anode potential difference can be eliminated from the root to stop the process of anode and cathode proceed. But once the anti-corrosion coating is damaged, exposed iron parts will accelerate localized corrosion. Therefore, anti-corrosion coating and cathodic protection combined rid of this method is the table, economical and effective.
Post time: Sep-11-2019
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