How should the surface of a spring be treated to prevent rust?
Release date:
2023-10-09
Most springs are used in various corrosive environments. Under the combined action of chemical and electrochemical corrosion, their surfaces suffer varying degrees of degradation, leading to premature failure. Therefore, corrosion protection is essential. Corrosion‑preventive treatment involves coating the spring surface with a corrosion‑resistant material to form a protective layer that isolates the spring from the corrosive environment, thereby achieving corrosion resistance.
There are three commonly used methods for preventing corrosion in springs: electroplating, oxidation, and painting. Electroplating is an effective way to create a protective coating on metal surfaces and is the primary method for corrosion protection of springs. It is characterized by strong adhesion of the plating layer, fine and dense crystalline structure, low porosity, uniform thickness, and excellent physical, chemical, and mechanical properties. Electroplating includes processes such as zinc plating, chromium plating, copper plating, tin plating, and nickel plating; among these, zinc plating is the most widely used.
The galvanized surface of springs is typically white or colored. Zinc exhibits virtually no change in dry air; however, in humid air or in water containing carbon dioxide, a white zinc oxide film forms, which provides some corrosion‑inhibiting protection. The zinc coating is suitable for use under a wide range of atmospheric conditions, but its corrosion resistance is limited in aqueous solutions containing acids, alkalis, or salts, as well as in purely marine atmospheres.
Galvanizing is characterized by low cost, a simple process, and good performance, making it widely used for corrosion protection of small and medium-sized springs exposed to atmospheric conditions. After galvanizing, springs must undergo passivation and dehydrogenation treatments to enhance their corrosion resistance and prevent hydrogen embrittlement. Small springs are particularly susceptible to hydrogen embrittlement, so extra care is required during pickling and electroplating. Oxidation treatment, also known as bluing or blackening, forms a protective layer of magnetic iron oxide on the spring surface, with a thickness of approximately 0.6 to 2 μm. However, due to its thinness and porous structure, this coating offers limited protection. Consequently, oxidation treatment is suitable only for corrosion protection of springs operating in mildly corrosive environments.
Because oxidation treatment is low-cost, features a simple process formulation, offers high production efficiency, and does not compromise the spring’s mechanical properties, it is widely employed for surface corrosion protection of small cold‑formed springs. In addition to oxidation, phosphating is another common method; the resulting phosphate coating is relatively stable under atmospheric conditions and exhibits 2 to 10 times greater corrosion resistance than oxidation. Painting is also one of the primary methods for protecting springs against corrosion, typically used for large and medium-sized springs—especially those formed by hot working and leaf springs. The paints commonly applied to springs include bituminous paint, phenolic acid paint, and epoxy paint. For certain critical springs, to enhance paint adhesion and corrosion resistance, a pre‑phosphating followed by painting process is often adopted. The conventional painting techniques are spray coating and dip coating; with advances in manufacturing technology, new processes such as electrostatic spraying are being promoted to improve productivity, paint utilization, and coating quality.
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WeChat ID: Lyx0608Ljl
Address: No. 68, Beiwai Street, Changning City, Hunan Province, China
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