Why Does The Color Of Galvanized Pipes Turn White?

Release time：

2025-12-31

The surface of the galvanized pipe turns white, mainly due to the combined effect of the chemical properties of the zinc layer on the surface and environmental factors. The following table can help you quickly understand the main causes and the corresponding key phenomena.

Main reason	Key phenomenon/mechanism	Conditions prone to occurrence
Normal oxidation	Zinc reacts with oxygen in the air to form a layer of white zinc oxide film.	All galvanized pipes will gradually undergo this process in the air, with a dry environment being the dominant factor.
Electrochemical corrosion (white rust)	Zinc reacts with water and carbon dioxide in a humid environment, forming white corrosion products such as basic carbonate zinc.	Occurring in a humid and poorly ventilated environment, after rain or being exposed to rain without timely drying.
Improper storage environment	Contact with chemical substances such as acids, alkalis and salts accelerates the corrosion and discoloration of the zinc coating	It is stored together with cement and chemicals in the warehouse. Outdoor industries pollute the environment.

Measures for Response and Prevention

After understanding the cause, we can take targeted measures to prevent and handle the problem of discoloration:

• Correct storage and placement:

Galvanized pipes should be stored in a dry, ventilated, and roofed warehouse. If they can only be stored outdoors, they must be raised and covered with waterproof fabric, ensuring "covering the top and padding the bottom", to avoid direct contact with the ground and rainwater. At the same time, they must not be mixed with corrosive materials such as acids, alkalis, salts, and cement.

• Deal with moisture promptly:

If the galvanized pipe is accidentally exposed to rain or gets damp, it should be dried on its surface as soon as possible or placed in a ventilated area to dry, to prevent prolonged moisture retention.

• Distinguish and handle the already whitened pipes separately：

◦ Uniform light white color:

If it is only a uniform layer of light white on the surface, this is usually a protective oxide film. Generally, it does not affect its anti-corrosion performance and service life, and no special treatment is required.

◦ Obvious white powder (white rust):

If there is a thick layer of white powder-like substance, it indicates that the corrosion has been quite severe. For minor white rust, you can use a hard brush or sandpaper to scrub it off and then apply anti-rust oil or zinc-based coating for protection. If the white rust is severe and the galvanized layer has been extensively damaged, it is recommended to consult a professional for assessment. In some cases, re-galvanizing or replacing the pipe may be necessary.

Summary

Overall, the whitening of galvanized pipes is a manifestation of the activity of the zinc layer. By understanding the causes and adopting the correct storage and maintenance methods, this problem can be effectively controlled.

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