What are the problems with the galvanizing process of seamless steel pipes?

　　The steel pipe manufacturer introduces to you the reasons and solutions for missing plating caused by hot-dip galvanizing of ASTM A53 seamless carbon steel pipes as follows:

　　1. The surface of the plated parts is not clean ⑴The surface of the plated parts contains paint, grease, and solder; it can be polished or scrubbed with relevant solvents. ⑵Iron oxide; pickling; continue pickling.

　　ASTM A53 Galvanized Seamless Carbon Steel Pipe is suitable for mechanical and pressure applications as well as general purpose use in steam, water, gas and air piping. It is suitable for welding and forming operations involving coiling, bending and flanging, subject to certain qualification requirements.

　　2. Pickling and operation:

　　⑴Acid and pickling. During washing, iron oxide (rust spots) is left on the surface of the plated parts; excessive pickling destroys the surface structure of the steel matrix, and the Si contained in it and a small amount of active metal refractory oxides are sprayed on the surface of the plated parts. Prevents the binding of iron and zinc. Or the plated piece absorbs soap due to pickling. At the same time, the soap expands and escapes due to thermal expansion, causing plating leakage. Solution: Strictly control pickling and master pickling time.

　　⑵ During pickling, the plated parts overlap and accumulate, resulting in missed cleaning, or due to the structure of the plated parts, concentration during pickling causes vortex air, resulting in missed cleaning. Solution: Spread the pickling turns out and turn frequently.

　　3. Auxiliary plating

　　⑴The additive concentration is low and the electroplating effect is not ideal; solution: adjust the additive concentration appropriately.

　　(2) The proportion of additives is improper and the zinc salt content is too high, which makes the additive salt film easy to absorb water and deliquesce, and the underlying materials layer into gases and quickly zinc, causing leakage. Solution: Adjust the additive ratio.

　　4. Zinc liquid composition and pot operation:

　　(1) The aluminum content in the zinc solution is too high, causing missed plating; solution: add zinc or use ammonium chloride to reduce the aluminum content;

　　⑵If the plated parts are put into the pot too slowly, the additives will be decomposed by heat and fail, resulting in missed plating. Adjust cooking speed appropriately.

　　⑶ The zinc immersion time is too short, which will prevent the subsequent iron-zinc reaction from proceeding.

　　(4) The zinc ash on the surface of the zinc liquid is not cleaned when the plated parts are put into the pot, so as to prevent the overheated zinc ash from burning the additives and causing leakage of plating.

　　⑸ When the plated parts are put into the pot, due to the process holes or structure, when the high-temperature gas in the plated parts is heated and escapes, the additives will be burned, causing missing plating. Solution: Sprinkle some ammonium chloride appropriately.

　　5. Coating materials

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

　　(2) The steel matrix contains too much carbon, or the steel produces too much iron carbide during the refining process, making it difficult for iron and zinc to combine, resulting in missed plating.

　　⑶ There are defects in the processing and molding of electroplating materials, resulting in cracks in the material, and the entry of acid, water and additives, resulting in missing plating.

　　ASTM A53 seamless carbon steel pipe must be washed with alkaline soap to remove oil before galvanizing, and then rinsed with fresh water. Next, it should be pickled to remove any lost scale and iron oxide, then dried before galvanizing.