The surface treatment process of 304 stainless steel butterfly screws directly affects its corrosion resistance, aesthetics and performance. The following is an analysis of some of its surface treatments.
Common surface treatment methods
Natural color treatment: Stainless steel wire is directly formed and then treated with shock or polishing to retain the original color of the metal without adding additional plating. The advantages are environmental protection, pollution-free and ROHS compliant, low cost, and suitable for general dry environments. The disadvantages are that weak magnetism is prone to occur in humid or high-salt environments, and the corrosion resistance is weaker than plating treatment.
Electroplating treatment
Nickel plating: It is divided into matte nickel, bright nickel, and black nickel. Matte nickel is anti-fingerprint and commonly used in industrial equipment; bright nickel has strong decorative properties and is suitable for furniture and electronic products; black nickel has both wear resistance and concealment.
Galvanizing: including blue zinc, color zinc, black zinc, and white zinc, which enhances rust resistance through passivation film, has a lower cost, but is less environmentally friendly than nickel plating.
Chrome plating: high gloss, super wear resistance, but the process is complicated and the cost is high, mostly used for high-end decorative parts.
Passivation treatment
Principle: Use an acidic solution to remove free iron ions on the surface to form a dense chromium oxide film, which significantly improves corrosion resistance.
Effect: Salt spray test can reach more than 500 hours (natural color treatment is only 72-200 hours), suitable for ships and chemical equipment.
Solution treatment (the function is to eliminate magnetism)
Applicable scenarios: Screws that become magnetic after cold processing (due to deformation martensite formation) are restored to austenite structure by heating to 1050℃ and then quenching with water to achieve non-magnetic properties.
Necessity: This process must be selected when the medical and electronic industries require a strictly non-magnetic environment.
Key process requirements and quality control
Plating thickness: Nickel plating layer must be ≥8μm, zinc plating layer must be ≥5μm, too thin can easily lead to protection failure.
Salt spray test standard
Natural color treatment: 72-200 hours; passivation treatment: ≥500 hours (ASTM B117 standard).
Magnetic control: Solution treatment is required after cold processing to ensure that the magnetism is ≤1.05 Gauss (medical industry requirements)
Suggestions for matching usage scenarios
Home appliances and furniture in conventional environments: natural color or nickel plating is sufficient
Ships and chemicals in highly corrosive environments: passivation treatment or 316 stainless steel material + plating
Medical equipment and laboratories without magnetic requirements: solution treatment + passivation composite process
Frequent manual operation: Plating can increase the surface hardness to prevent butterfly wing deformation
