Medical springs: surface treatment of spring equipment to extend service life

The corrosion of springs can be divided into chemical corrosion and electrochemical corrosion according to the type of reaction. They are all the result of the change of metal atoms on the spring surface or the change of electron gain and loss into ionic state.

If the metal on the spring surface only reacts with the surrounding medium, and the spring causes corrosion, it is called chemical corrosion. For example, the spring oxidizes in a particularly dry atmosphere to form an oxide film, and the spring chemically changes with the liquid or impurities in the liquid in a non electrolyte liquid, which belongs to chemical corrosion.

If the spring contacts with the electrolyte solution, the corrosion caused by the micro battery is called electrochemical corrosion. For example, the spring is in contact with acidic or salt solutions, which are all electrolytes. Electrodes with different potential differences are formed due to defects or impurities on the spring surface, so that the spring is continuously subject to electrolytic corrosion. For example, the spring is in a humid atmosphere, and the water vapor in the atmosphere condenses into a water film or water droplet on the spring surface, In addition, corrosive gases in the atmosphere (such as sulfur dioxide and hydrogen sulfide in industrial waste gas or salt spray in marine atmosphere) dissolve in water film or water droplet to form electrolyte. In addition, impurities or defects of the spring metal can also form electrodes with different potential differences, and the spring can also produce electrolytic corrosion. These are electrochemical corrosion.

The chemical corrosion of spring is small and slow, while the electrochemical corrosion is main and common. But generally speaking, chemical corrosion and electrochemical corrosion exist at the same time.

Medical springs are often corroded by the surrounding media in the process of manufacturing, storage and use. As the spring works by the elastic force, the elastic force will change after the spring is corroded and lose its function. Therefore, preventing the corrosion of the spring can ensure the working stability of the spring and prolong its service life.

The anti-corrosion method of spring generally adopts protective layer, which can be divided into metal protective layer, chemical protective layer, non-metallic protective layer and temporary protective layer according to the nature of the protective layer. The first three methods are mainly introduced here.