What are the surface treatments in the manufacturing process of stainless steel torsion springs

As a key precision mechanical component, stainless steel torsion springs are widely used in automobiles, electronics, aerospace and other industries. Its manufacturing process requires extremely high requirements for the control of material composition and the accuracy of the molding process. At the same time, surface treatment technology also plays a vital role in improving the corrosion resistance, wear resistance, aesthetics and service life of the spring.

Passivation treatment
Passivation treatment is a common treatment method for the surface of stainless steel torsion springs. Through a chemical reaction, a dense passivation film is formed on the surface of the spring, mainly composed of chromium oxide. This film can effectively block the contact between external corrosive media (such as oxygen and moisture) and the spring base metal. Commonly used passivation solutions include nitric acid and citric acid. Nitric acid passivation can generate a chromium-rich oxide film on the surface of the spring. This kind of film has excellent self-healing ability. Even when the film layer is partially damaged, the surrounding chromium elements can quickly react with oxygen to re-form a protective film, thereby significantly improving the corrosion resistance of the stainless steel torsion spring.

electropolishing
Electropolishing is a surface treatment method based on electrochemical principles. In the electrolytic cell, the spring serves as the anode. By applying appropriate voltage and current, the microscopic convex parts of the spring surface are preferentially dissolved to achieve a smooth and bright effect. After this treatment, the surface roughness of the spring is significantly reduced, which not only improves the appearance, but also further enhances the corrosion resistance of the spring due to the enhanced smoothness of the surface, which makes it difficult for dirt and impurities to adhere. At the same time, electrolytic polishing helps to improve the fatigue performance of the spring and reduce surface microscopic defects, thereby reducing stress concentration points, allowing the spring to reduce the risk of cracks and other fatigue damage when it withstands repeated tension and compression.

shot peening
Shot peening is mainly used to improve the surface strength and fatigue resistance of stainless steel torsion springs. This process involves high-speed injection of projectiles (such as steel shot or glass beads) into the spring surface, causing it to undergo a certain degree of plastic deformation and form a cold work hardened layer. This hardened layer can generate residual compressive stress, which can partially offset the tensile stress when the spring is working, thereby reducing the actual tensile stress level on the surface of the spring, effectively extending its service life, and reducing failures such as fracture due to fatigue.

Paint treatment
In some application scenarios that require high protection of stainless steel torsion springs or have special color requirements, painting is an effective solution. Painting can form an organic protective film on the surface of the spring to isolate air and moisture, thus improving the corrosion resistance of the spring. Choosing the right paint is crucial, for example, epoxy paint is widely used due to its excellent adhesion and corrosion resistance. Before painting, proper pre-treatment (such as degreasing and phosphating) of the spring surface is necessary to ensure that the paint can adhere firmly to the surface. This processing method not only allows the selection of different colors of paint according to actual needs, but also ensures mechanical function while meeting other requirements such as aesthetics.