What Is The Alkali Reversion Phenomenon Of Galvanized Pipes?

In the actual application process of galvanized pipes, alkali reversion sometimes occurs, which not only affects the appearance but also may affect the protective performance and service life of the pipe. The formation of alkali reversion is a complex electrochemical and chemical process, involving the corrosion of the galvanized layer and the interaction of environmental factors. The following is an analysis of the reasons for the alkali reversion of galvanized pipes:

1. Galvanized layer corrosion

Chemical reaction: The oxide in the galvanized layer reacts with water vapor, causing the galvanized layer to corrode, which in turn causes alkali reversion.

Electrochemical corrosion: In humid air, the local surface of the galvanized layer will undergo electrochemical corrosion due to the lack of free-flowing air on the surface, forming white rust.

2. Environmental factors

Humid environment: Galvanized parts are prone to condensation in a humid environment, and after reacting with gases such as oxygen and carbon dioxide, they produce corrosive aqueous solutions, resulting in alkali reversion.

Chemical gas: The presence of chemical gases such as hydrogen sulfide and sulfur dioxide will aggravate the corrosion of the galvanized layer and promote the occurrence of alkali reversion.

3. Galvanizing layer quality

Galvanizing layer thickness: When the zinc layer is not thick enough, its protective ability is reduced, and it is more prone to corrosion and alkali return.

Galvanizing layer uniformity: If the zinc layer is uneven, the protective ability of some parts is weak, which makes it easy to become the starting point of alkali return.

4. Storage conditions

Dense stacking: The galvanized parts are tightly stacked, resulting in poor air circulation, which increases the risk of alkali return.

Ventilation and drying: Proper storage conditions, such as good ventilation and dry environment, can reduce the possibility of alkali return.

5. Plating solution composition

Sodium hydroxide content: The high sodium hydroxide content in the plating solution will accelerate the chemical dissolution of the zinc anode and affect the quality of the zinc coating.

6. Cleaning treatment

Water washing and pickling: Water washing or pickling after hot-dip galvanizing can remove residual alkaline metal oxides on the metal surface and reduce the risk of alkali return.

7. Protective measures

Personal protection: When dealing with the problem of hot-dip galvanizing alkali return, personal protection measures should be taken to avoid acid and alkali from causing harm to operators.

In addition, after understanding the above reasons for alkali reversion, 

the following measures can be taken to prevent and deal with the alkali reversion phenomenon of galvanized pipes:

Ensure the galvanized layer's thickness and uniformity and improve the galvanizing quality.

Improve storage conditions, keep ventilation and dry, and avoid close accumulation of galvanized parts.

Control the composition of the plating solution to avoid excessive sodium hydroxide content.

Regularly perform cleaning and maintenance, including water and acid washing, to remove substances that may cause corrosion.

Once the alkali reversion phenomenon is found, measures should be taken in time, such as placing the plated parts in a dry and ventilated place to avoid further development of alkali reversion.

Generally speaking, the alkali reversion of galvanized pipes results from the combined effect of corrosion of the galvanized layer and adverse environmental factors. By improving the quality of galvanizing, improving storage conditions, and regular maintenance, the alkali reversion problem can be effectively prevented and dealt with, thereby extending the service life of the galvanized pipe and maintaining its good protective performance.