The five elements commonly used in steel that affect the welding performance of steel are carbon, silicon, manganese, phosphorus, and sulfur.

1. Carbon: As the carbon content in steel increases, the yield point and tensile strength increase, but the plasticity and impact resistance decrease. When the carbon content exceeds 0.23%, the welding performance of the steel deteriorates. Therefore, the carbon content of low-alloy structural steel used for welding generally does not exceed 0.2%. High carbon content will also reduce the steel's resistance to atmospheric corrosion. High-carbon steel in open-air material yards is prone to rust. In addition, carbon can increase the cold brittleness and aging sensitivity of steel.
2. Silicon: Silicon is added as a reducing agent and deoxidizer during the steelmaking process, so calm steel contains 0.3% silicon. If the silicon content in steel exceeds 0.6%, silicon is considered an alloying element. Silicon can significantly increase the elastic limit, yield point, and tensile strength of steel, so it is widely used as spring steel. Adding 1.2% silicon to quenched and tempered structural steel can increase the strength by 15-20%.
3. Manganese: In the steelmaking process, manganese is a good deoxidizer and desulfurizer. Generally, steel contains 0.3-0.5% manganese. When more than 0.7% is added to carbon steel, it is called "manganese steel". Compared with ordinary steel, the steel has not only sufficient toughness, but also higher strength and hardness, improves the hardenability of steel, and improves the hot processing performance of steel.
4. Phosphorus: Phosphorus is a harmful element in steel, which increases the cold brittleness of steel, deteriorates welding performance, reduces plasticity, and deteriorates cold bending performance. Therefore, the phosphorus content in steel is usually required to be less than 0.045%, and the requirement for high-quality steel is lower.
5. Sulfur: Sulfur is also a harmful element under normal circumstances. It makes steel hot and brittle, reduces the ductility and toughness of steel, and causes cracks during forging and rolling. Sulfur is also not good for welding performance and reduces corrosion resistance.

The first anti-corrosion of steel corrugated culverts is hot-dip galvanizing. The theoretical service life of hot-dip galvanizing is about 100 years. In order to achieve a better anti-corrosion effect, we spray asphalt inside and outside the pipe wall, which is secondary anti-corrosion. Secondary anti-corrosion should be applied twice with a mixture of asphalt and petroleum. From the appearance, the inside and outside of the pipe wall are evenly painted into a black pipe, but it must be installed after the asphalt is dried. The thickness of the asphalt coating is kept within 0.4mm-0.5mm. 

The painting method is as follows: 
1: Thick asphalt coating containing asbestos fiber: The solvent of the coating is high-quality asphalt, and the content of asbestos powder is greater than or equal to 30%. The spraying method can be sprayed with air pressure or brushed with a brush. The thickness of each spray layer is 7mm-8mm, and the spraying amount is about one kilogram per square meter. The surface of the sprayed object should be particularly dry and free of oil stains, apply to the corrugated culvert soaked in wastewater or below the normal water level.

2. Asphalt and kerosene mixture coating: The ratio of asphalt and kerosene is 54:46. When using this coating, it should be brushed twice to make the total thickness of the coating layer reach 0.4mm--0.5mm, and the amount of coating is 0.6 kg per square meter. If conditions permit, spraying with a spray gun will have a better effect, apply it on the corrugated culverts that are soaked in wastewater or below the normal water level.

1. Use measuring tools
First, we can use measuring tools to check the thickness of stainless steel pipes. Common measuring tools are micrometers, vernier calipers, and ultrasonic thickness gauges. Among them, micrometers and vernier calipers are suitable for stainless steel pipes with smaller diameters, while ultrasonic thickness gauges are suitable for stainless steel pipes of various diameters.
The method of using the measuring tool is to first place the two legs of the measuring tool on both sides of the stainless steel pipe, making sure that they are perpendicular to the surface of the pipe. Then, read the scale value on the measuring tool to get the thickness of the stainless steel pipe. It should be noted that when using the measuring tool, the accuracy and precision of the tool must be ensured to obtain accurate measurement results.
2. Cutting method measurement
In addition to using measuring tools, we can also use the cutting method to measure the thickness of stainless steel pipes. This method is suitable for situations where more accurate thickness values need to be obtained.
The steps of the cutting method are to first select a section of stainless steel pipe and cut it into two sections using a cutting tool. Then, use a microscope or magnifying glass to observe the cross-section at the incision and measure the thickness of the cross-section. Finally, the average thickness of the two sections of stainless steel pipe is used as the thickness of the entire stainless steel pipe.
It should be noted that the cutting method will cause some damage to the stainless steel pipe, so it is suitable for testing or situations where precise values are required, but not suitable for routine inspection.
3. Ultrasonic thickness measurement method
Ultrasonic thickness measurement is a non-destructive measurement method suitable for stainless steel pipes of various diameters and wall thicknesses. It calculates the thickness of the stainless steel pipe by sending ultrasonic pulses and using the difference in the propagation speed of ultrasonic waves in different materials.
In specific operations, the ultrasonic thickness gauge is used to place the sensor on the surface of the stainless steel pipe and send ultrasonic pulses. After the pulse passes through the stainless steel pipe, it will return and be received by the ultrasonic thickness gauge. By calculating the propagation time and speed of the pulse, the ultrasonic thickness gauge can accurately calculate the thickness of the stainless steel pipe.