First: Causes of alkali reflux (white rust, black spots) of galvanized steel pipes
1. Principle of white rust formation of galvanized steel pipes
When galvanized steel pipes are tightly stacked and placed in humid air since there is no free-flowing air on the surface of the product, the surface of the zinc layer will undergo electrochemical corrosion to form white rust. As the condensed water attached to the surface of the zinc layer fuses with oxygen, carbon dioxide, hydrogen sulfide, sulfur dioxide, oxides, and other chemical gases, a corrosive aqueous solution will be produced and attached to the surface of the zinc layer to form an electrolyte, and this electrolyte will produce electrochemical corrosion with the zinc layer, thereby producing white rust in the form of powdery white dots (zinc oxide) visible to the naked eye. The secondary and tertiary oxidation products of white rust form a local black surface, which is collectively referred to as alkali reflux.
2. Effect of white rust on galvanized steel pipes
Since the volume of metallic zinc increases by 3 to 5 times when it is converted into zinc oxide or zinc hydroxide, the volume of white rust formed is larger, which makes the degree of white rust corrosion appear to be much more serious than the actual situation, seriously affecting the appearance of the zinc layer, but they only cause a small loss of zinc on the surface.
3. White rust treatment of galvanized steel pipes
A large amount of white rust may appear on the surface of galvanized steel pipes, but the actual corrosion of the zinc layer is relatively mild. In most cases, the appearance of white rust does not indicate that the zinc layer has been seriously damaged. After white rust occurs, the galvanized steel pipes should be spread out to make their surface dry quickly. In summary, due to factors such as weather, transportation, and storage, the alkali-reversal phenomenon is common in galvanized steel pipes in summer. As long as the zinc layer after corrosion is higher than the standard value, it will not have any impact on the service life of the product.

Second: Precautions for galvanized steel pipes
1. All galvanized steel pipes will produce white rust in humid, high temperatures, poor air circulation, and corrosive environments. Products that are very prone to white rust: After water accumulates in tightly packaged and sealed products such as angle steel, flat iron, square tubes, and round tubes, the weather is hot and humid, and the water accumulates and humidifies, which makes it easy for galvanized steel pipes to alkali.
2. After arriving at the destination, the galvanized steel pipe should be stored in a warehouse with good air circulation, and should not be stacked in places with harmful gases and dust.
3. If there is slight white rust or spots on the surface, it should be disassembled and dried immediately, and ventilated until the white rust turns into powder and then brushed off with a brush in time.
4. In a humid and sultry environment, try to store it indoors to keep it ventilated and dry, and avoid direct contact with wet soil when stacking.
5. Galvanized steel pipes are not afraid of high temperature, humidity, or concentrated stacking, but they are afraid of all three at the same time, that is, concentrated stacking in a humid and sultry environment.
Only galvanized steel pipes that have been passivated are good.