What to do if 316L thick-walled stainless steel pipe is corroded?

316L thick-walled stainless steel pipes are highly valued for their corrosion resistance, impact resistance, and high-temperature durability, making them commonly used in industries such as medicine, chemicals, food, light industry, chemical machinery, industrial pipelines, and mechanical parts. These thick-walled pipes are also essential in the production of exhaust systems and various basic pipelines. However, over time, these pipes may experience corrosion. So, what should be done if a 316L thick-walled stainless steel pipe becomes corroded?

When 316L thick-walled stainless steel pipes corrode, the anodic oxidation layer is damaged, while the negative electrode remains intact. To prevent this, one method is to maintain the pipe as the negative electrode throughout its use, which helps prevent corrosion. This corrosion prevention technique is known as pipeline cathodic protection. It acts as a safeguard, using movable metal materials as a protective layer, which, in turn, protects the metal parts without destroying the anodic oxidation layer. This method can also be scientifically refined to improve its effectiveness.

Cathodic protection can be broken down into two methods: protective film method and electrical equipment protection method.

Protective Film Method:

This method involves using a relatively active alloy as a protective film, which is either inserted onto the surface of the stainless steel pipe or connected to it by wire. The protective alloy and the stainless steel pipe form two sides of a galvanic cell. In this setup, the active metal (protective film) undergoes anodic oxidation in the battery, becoming oxidized and damaged by corrosive elements, while the stainless steel pipe acts as the cathode. This results in the cessation or weakening of the corrosive process, protecting the steel pipe from further damage. When the protective film begins to rust, it can be replaced with a new one.

Electrical Equipment Protection Method:

This method works similarly by attaching the stainless steel pipe to the negative terminal of a power supply, while the positive terminal is connected to an anodic oxidation connection. This setup creates a protective mechanism where the stainless steel pipe remains protected from corrosion. Over time, as the protective metal material corrodes, it shields the main material, similar to how zinc is used to protect gas steam boilers or the propellers of ships. Zinc, being more reactive than iron, gradually corrodes to protect the equipment.

This method of corrosion protection is also referred to as sacrificial anode protection or cathodic protection. For example, in marine applications, zinc blocks are embedded around ship propellers, and similarly, zinc is used in gas steam boilers. Zinc, being more reactive than iron, corrodes in place of the metal parts, preventing them from deteriorating. This principle is also applied in the electrolysis process, where the electrode connected to the negative terminal of the power supply remains intact, as it does not lose electrons, and thus, the 316L thick-walled stainless steel pipe is not corroded.

In summary, the use of external currents to connect the stainless steel thick-walled pipe to the negative terminal of a switching power supply, and setting the positive terminal to anodic oxidation, helps to maintain the protection of the pipe. This technique can be applied to older pipes, railway tracks, and other items that experience slow corrosion. The method works similarly to the protective film method, offering effective corrosion prevention and extending the service life of the steel pipe.