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Principle of galvanized sheet anticorrosion

- Jul 27, 2018 -

Principle of galvanized sheet anticorrosion

1. What are the characteristics of steel corrosion?

   When steel leakage in the atmosphere, the main occurrence of dry corrosion, wet corrosion and wetting corrosion and other forms.Dry corrosion of iron and steel refers to the corrosion of continuous electrolyte water film on the surface of the steel belt in an atmosphere with relative humidity less than 30%.In this pity!In this case, the corrosion rate of steel is very slow, but this kind of environment condition is less.

     Humid corrosion of steel refers to corrosion of steel in an atmosphere with relative humidity greater than 30% and less than 100%.In this case, there is dust on the surface of iron and steel, and there are microholes and cracks in the rust layer, resulting in micro-adsorption, forming water film invisible to the naked eye. Electrolysis and chemical corrosion occur under the water film, and the corrosion rate is relatively fast.Wetting corrosion of iron and steel refers to the corrosion of solidified, visible water film on the surface of steel in humid atmosphere with relative humidity greater than 100%.Under such conditions, the water film on the surface of steel is thicker, which makes the diffusion of oxygen to the surface of steel slow and reduces the rate of corrosion.


2.What are the characteristics of zinc corrosion?

   Zinc is a more active metal element than iron and is more prone to oxidation and corrosion, but because its corrosion reflects the different properties of the products, the corrosion of zinc is fundamentally different from that of steel.

   Zinc also reacts with oxygen in the air in a dry, water-free environment to form a chlorination front.This is different from "red rust" after iron oxidation, whose color is white, so it is called "white rust". The expression is as follows: 2Zn+ 02-2zno

   Zinc in moist air is subject to electrochemical corrosion caused by aerobic participation, and also produces zinc oxide. 002 in the air will be further reflected with 2NO, resulting in ZNC03, whose color becomes slightly black, and a black spot is formed on the surface of zinc, so it is called "shining spot".

   In this way, in the atmospheric environment, the surface of zinc is covered with an oxide film composed of zinc oxide, zinc carbonate and zinc hydroxide, which is relatively dense and has good adhesion performance. It can isolate the external oxygen from the internal tissue and prevent the internal zinc substrate from being oxidized by samples.According to the corrosion loss ratio, the corrosion loss of steel is 15"30 times that of zinc.However, the corrosion properties of zinc in polluted atmosphere are greatly affected.


3. Why can zinc prevent corrosion?

   The significance of hot galvanizing is that there is a layer on the surface of the steel belt, and the corrosion resistance is greatly improved after the zinc layer is covered, which can save materials and resources and bring into full play good economic and environmental benefits.