As we all know, galvanized is a zinc coating on the surface of steel, in order to prevent rust and corrosion, it has a longer lifespan than paint to prevent rust, usually lasts for 50 years or more, cost of use and maintenance will be lower.
Of course, when considering rust and corrosion resistance, some project leaders also consider stainless steel, if you want to know more about the comparison of galvanized steel and stainless steel in terms of rust and corrosion resistance, please check this article : Galvanized Steel vs Stainless Steel: What is The Difference?
How does galvanized steel prevent rust?
Generally, galvanizing is divided into electro-galvanizing and hot-dip galvanizing. Considering economy and environmental protection, hot-dip galvanizing is a common galvanizing method.
After the steel is galvanized, the surface is covered with a layer of zinc coating, which separates the steel from the atmosphere, avoids direct contact and corrosion of the steel by the atmosphere, and is protected. As for the coating of zinc on the surface of steel, due to the relatively strong chemical activity of zinc, a thin and dense layer of zinc carbonate will be formed in the air at room temperature to protect the zinc itself from further oxidation.
Therefore, galvanized steel, both the zinc on the surface and the steel itself, are protected from rust and do not need to be painted with anti-rust paint. Only when the galvanized layer is damaged (such as welding and the coating at the joint is burned) and the steel is exposed to the air and loses the protection of the galvanized layer, is it necessary to reapply anti-rust paint.
What are the factors that induce rust in steel?
- Relative humidity above 60%
- Sodium chloride (salt) in water or air
- Wet or soaked environments
- Increase in temperature when combined with corrosive factors like humidity and industrial pollution
- Acids; particularly sulfur acids produced by (1) hydrogen sulfide – from volcanoes, hot springs, natural gas, and sewer gas – and (2) sulfur dioxide pollution in the urban atmosphere
- Strong Alkalis
- Plasters and cements (especially Portland cements) containing chlorides and sulfates
- Acid rainwater runoff from roofs with wood shingles
- Moss and lichen
- Contact between galvanized items and copper, pure iron, or steel causes galvanic corrosion. Galvanic (electrochemical) corrosion is an electrolytic corrosion reaction between the zinc coating and dissimilar metals when in the presence of an electrolyte such as rain, dew, fog or condensation.
- Acidic food and drinks
How long does galvanized steel last without rusting?
Although the surface of the steel is galvanized and has corrosion resistance, local rust spots will also appear under complex environmental erosion for a long time. Galvanized steel typically lasts 50 years or more. Galvanized steel rusts because zinc is easily soluble in acid and alkali, so it is called an amphoteric metal. Zinc changes little in dry air. In humid air, a dense basic zinc carbonate film will form on the zinc surface. In atmospheres containing sulfur dioxide, hydrogen sulfide and marine atmospheres, zinc has poor corrosion resistance. Especially in atmospheres with high temperature, high humidity and organic acids, the zinc coating is easily corroded.
The standard electrode potential of zinc is -0.76V. For steel substrates, zinc coating is an anodic coating. It is mainly used to prevent corrosion of steel. Its protective performance is closely related to the thickness of the coating.
After the zinc coating is passivated, dyed or coated with light protection agent, its protection and decoration can be significantly improved. Zinc will oxidize in the air and white rust will form on the surface, which is normal.
It also depends on whether the surface treatment of galvanized steel is hot-dip galvanized or electro-galvanized. If it is hot-dip galvanized, because the zinc layer is relatively thick, the formation of white rust will not affect the normal warranty, because the oxidation speed of zinc in the air is very slow. It’s hard to say if it’s electro-galvanized. As long as the rust is not visible it will not affect. Therefore, when using galvanized steel grating, be careful not to put it in a humid place. If the weather is too hot and not ventilated, it will easily become moldy. In winter, it will last longer.
It also depends on whether the surface treatment of galvanized steel is hot-dip galvanized or electro-galvanized. If it is hot-dip galvanized, because the zinc layer is relatively thick, the formation of white rust will not affect the normal warranty, because the oxidation speed of zinc in the air is very slow. It’s hard to say if it’s electro-galvanized. As long as the rust is not visible it will not affect. Therefore, when using galvanized steel grating, be careful not to put it in a humid place. If the weather is too hot and not ventilated, it will easily become moldy. In winter, it will last longer.
Best Galvanized Steel Manufacturer and Supplier in China
As China galvanized steel manufacturer and supplier, Metal in China(HUA ZHU) Co., Ltd provides a series of products such as galvanized steel sheets, galvanized steel coils and galvanized steel pipes that comply with ASTM American standards, including DX51D/DX52D/DX53D and DX54D, etc., with zinc spray coating thickness support Customization (z20-z275), the size of galvanized sequins can be customized (regular galvanized flowers, small galvanized flowers and no zinc flowers).
You can learn more about our galvanized materials and hot-dip galvanizing services on our website, and contact us using this link: www.metal-in-china.com/contact-us.
Metal in China(HUA ZHU) Co., Ltd., established in 1999, is a leading manufacturer and supplier dedicated to carbon steel, galvanized steel and stainless steel materials and products. We provide many overall metal solutions for customers from all walks of life at home and abroad, such as military equipment suppliers, design agencies, construction contractors, metal product distributors, elevator manufacturers, and home appliance manufacturers.
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