Why 4.762mm 430 Stainless Steel Balls are Suitable for Nail Polish Bottles:

1. Primary Function: Mixing/Agitation: The small steel ball (agitating ball or mixing ball) is placed inside the bottle to help mix the nail polish thoroughly when the bottle is shaken. This breaks up settled pigments and ensures a consistent color and texture before application. The 4.762mm size is common and effective for this purpose in standard nail polish bottles.
2. Corrosion Resistance (Adequate for the Environment): 430 stainless steel is a ferritic grade containing chromium (typically 16-18%). This chromium forms a passive, protective oxide layer on the surface, providing good resistance to:
   • Atmospheric Corrosion: Resists rusting from exposure to air.
   • Mild Chemicals: Resists many organic solvents and mild acids/bases found in nail polish formulations under typical use conditions (intermittent contact, not constant immersion). While not as corrosion-resistant as 304 or 316 grades, it is generally sufficient for the nail polish environment.
3. Non-Reactivity: The passive chromium oxide layer minimizes chemical reactions between the steel ball and the nail polish solvents, resins, and pigments. This helps prevent contamination of the polish (like discoloration or degradation) and avoids the ball itself corroding significantly during the product's shelf life.
4. Hardness and Durability: 430 stainless steel is relatively hard and durable. It can withstand the constant impact against the glass bottle walls during shaking without deforming, fragmenting, or excessively wearing down, ensuring it performs its mixing function effectively over time.
5. Cost-Effectiveness: Compared to higher-grade austenitic stainless steels like 304 or 316, 430 is generally less expensive. This makes it an economically viable choice for a component like a mixing ball, where its specific properties are adequate for the application.
6. Industry Acceptance: The use of 430 stainless steel balls (often in the 4mm to 5mm / 3/16 inch size range) is a well-established practice within the cosmetics industry for nail polish bottles. Its performance and cost profile meet the requirements for this specific component.