Weld Nut Surface Treatment Technology And Its Advantages

Weld nut surface treatment technology and its advantages

The welding nut may seem inconspicuous, but it directly determines the firmness of the welded structure. Many people have discovered in actual work that some of the same nuts are very strong when welded on, while others are easy to fall off or rust. The problem lies in the surface treatment.

Advantages and options of electroplating processes

The surface of the welding nut is covered with a metal film. This process is called electroplating. In 2025, there was a domestic auto parts factory. The test data it gave showed that welding nut surface treatment technology and its advantages. Galvanized nuts can last 72 hours without rusting in the salt spray test, but ordinary nuts only last 8 hours. The cost of zinc coating is relatively low, with a processing fee of about 3 to 5 yuan per kilogram, so it is suitable for mass production.

In the field of construction machinery, welding nuts on excavator booms often have to withstand vibration and friction. Nickel plating is harder and more wear-resistant than zinc. There is a heavy machinery factory in Shanghai. Comparative experiments conducted in 2024 showed that the life of nickel-plated nuts is more than twice as long as that of galvanized nuts. Chrome plating is the brightest and has a good decorative effect. It is more common in home appliances and outdoor equipment.

The physical effects of sandblasting

Use high-pressure airflow to hit fine sand onto the surface of the nut. This action is called sandblasting. It can remove oxide scale and rust, thereby making the surface rough. The rough surface will be easier to fuse with the base material during welding. A steel structure company in Changzhou, Jiangsu has conducted relevant tests. For nuts of the same specifications, the welding strength after sandblasting is 30% higher than that of untreated nuts.

The sandblasting process is very fast . Whether the surface of the wear-resistant steel plate rivet weldment needs to be treated , a worker can process approximately two thousand nuts in one hour. The scale of equipment investment is not huge. A set of small sandblasting machine costs about 20,000 yuan. For those welded parts that require high strength, such as bridges and building steel structures, sandblasting is almost a necessary process. However, the nuts after sandblasting must be used as soon as possible, otherwise they will easily oxidize again.

Chemical principles of phosphating treatment

When the nut is soaked in chemical solution for phosphating, a layer of phosphate film will be formed on the surface. This film is extremely thin, only a few microns, but it can greatly improve the adhesion of the paint. Experimental data from a fastener factory in Ningbo, Zhejiang shows that the porosity of phosphated nuts dropped by 45% during welding, and cracks were also significantly reduced.

The temperature requirements for phosphating treatment are not very high, usually in the range of 40 to 60 degrees. The cost of potion per liter is about 20 cents, which is cheaper than electroplating. The body color of the phosphating film is gray-black, which is not bright but practical. Many of the welding nuts on the automobile chassis are phosphated because it will not affect the conduction of the welding current. But what needs to be noted is that the phosphated nut cannot be stained with oil, otherwise the welding effect will become worse. Is there anything wrong with that?

Protective effect of coating technology

The coating is applied to the nut by spraying or dipping. Common coating materials include epoxy resin, polyurethane and Teflon. The epoxy resin coating is the hardest and has scratch resistance and is suitable for outdoor equipment. Polyurethane has good elasticity and can resist impact. Teflon is the smoothest and is not easy to adhere to things.

In 2025, there was an outdoor lighting factory in Shenzhen, Guangdong. Its case showed that after using epoxy-coated welding nuts, the rust rate of the products when exposed to coastal high salt spray environments dropped from the original 15% per year to less than 2%. The coating has the function of adjusting the color, for example, it can be black, gray or yellow, so that different specifications can be easily distinguished. However, the thickness of the coating must be controlled well. If it is too thick, it will affect the matching accuracy of the thread.

Applicable scenarios for different methods

Electroplating is suitable for ordinary industrial environments, its cost is low, and its anti-rust effect is sufficient to meet demand. Sandblasting is suitable for high-strength welding, such as pressure vessels and heavy-duty structures. Phosphating is suitable for workpieces that will be painted later, and its adhesion is good. The coating is suitable for outdoor and humid environments, such as ships, port equipment, and sewage treatment plants.

The specific choice must refer to three factors. One is whether the working environment is humid, the other is whether the welding strength requirements are high, and the third is how much the budget is. If the surface of the wear-resistant steel plate rivet weldment in a dry indoor environment needs to be treated , then electroplating is sufficient. If it is located in an environment such as the seaside or a chemical plant, it is recommended to use coating or chrome plating. If the welded parts bear a very large force, then the combination of sandblasting and phosphating will have the most ideal effect.

Surface treatment cost comparison

At the beginning of 2026, the quotation given by the market shows that for each ton of welding nuts, the electroplating cost is approximately in the range of 500 yuan to 800 yuan, the sandblasting cost is in the range of 300 yuan to 500 yuan, the phosphating cost is 200 yuan to 400 yuan, and the coating cost is 800 yuan to 1,500 yuan. Among them, the cost of phosphating is the lowest, and the cost of coating is the highest. However, the protective effect of the coating is the best and its service life is also the longest.

From a long-term perspective, although the coating is expensive and whether the surface of the wear-resistant steel plate rivet weldment needs to be treated , it does not require maintenance for ten years. The cost of electroplating is relatively low, and it may need to be replaced in three to five years. The labor costs involved in repairs are often much higher than the material costs. Therefore, many engineers will calculate an account: if the equipment is easy to replace, then use electroplating; if the disassembly and installation are extremely cumbersome, then use coating in one step.

Surface treatment is not a process that can be ignored, but it is a key step to ensure welding quality and product life. What kind of surface treatment does the weld nut you currently use have? Have you ever encountered rust or falling off? Feel free to share your actual experiences in the comment area, and don’t forget to like and forward it to more colleagues in need.