The reasons for the leakage of hot-dip galvanizing of seamless steel pipes

When the seamless steel pipe is processed by the hot-dip galvanizing process, sometimes there will be leakage of plating. What is the reason for the occurrence of such a seamless pipe? Let's take a look at the reasons for the leakage of plating and how to solve the leakage of seamless steel pipes.

1. The surface of the seamless steel pipe is not clean

(1) The surface of the seamless steel pipe contains paint, grease, and welding; it can be polished or scrubbed with related solvents.

⑵ iron oxide; under pickling; continue to pickling.

2. Pickling and operation:

⑴ owe, over pickling. Under-pickling will leave iron oxides (rust spots) on the surface of the plated parts; over-pickling will destroy the surface structure of the steel substrate, and the Si and a small amount of active metal refractory oxides contained in it will adhere to the surface of the plated parts. Blocks the combination of iron and zinc. Or due to over-pickling, the plated parts absorb hydrogen, and when galvanized, hydrogen and other thermal expansion escape and leak plating. Solution: Strictly control pickling and grasp the pickling time.

(2) During pickling, the plated parts are superimposed and accumulated, resulting in leakage cleaning, or due to the structural reasons of the plated parts, the eddy gas is caused by the neglect of flipping during pickling. Solution: Spread the pickling as far as possible and turn it frequently.

3. Plating process

(1) The concentration of the auxiliary agent is low, and the plating effect is not ideal; Solution: Adjust the concentration of the appropriate auxiliary agent.

(2) Improper ratio of additives and high content of zinc salts make the salt film of the additives easy to absorb water and deliquescence, and the hydroxides decompose into gas and explode zinc, resulting in leakage plating. Solution: adjust the ratio of additives.

4. Zinc liquid composition and pot operation:

(1) The aluminum content in the zinc solution is too high, resulting in leakage plating; the solution: reduce the aluminum content by adding zinc or using ammonium chloride consumption;

(2) The speed of the seamless steel pipe is too slow, and the auxiliary agent is decomposed and invalidated by heat, causing leakage plating. Adjust the cooking speed appropriately.

(3) The zinc immersion time is too short so that the iron-zinc reaction can be carried out in the future,

⑷The zinc ash on the zinc liquid surface is not cleaned when the seamless steel pipe is placed in the pot, which makes the overheated zinc ash burn the auxiliary and leak plating.

⑸ When the seamless steel pipe is placed in the pot, due to the process hole or structure, when the high-temperature gas in the seamless steel pipe is heated and escaped, the auxiliary agent will be burned, causing leakage plating. Solution: Sprinkle some ammonium chloride in an appropriate amount.

5. Plating material

(1) The surface of the seamless steel pipe contains refractory oxides of elements such as silicon and aluminum, which prevent the reaction of iron and zinc.

(2) The matrix of the seamless steel pipe contains too much carbon, or the steel produces too much iron carbide during the refining process, which makes the combination of iron and zinc difficult, resulting in leakage plating.

(3) The processing and forming defects of the seamless steel pipe material cause the material to rot and crack, and the acid, moisture, and additives enter, causing leakage plating. At present, there is no good solution except for ammonium chloride.