Does the plating darken? Causes of sulfide.

Does plating darken? Causes of sulfide and prevention measures.

Plated parts can turn black over time. Have you ever experienced this? This phenomenon is common with silver and copper plating, and the cause may be sulfide formation. Sulfide formation is a chemical reaction where metals react with sulfur components to create metal sulfides. Examples: - Silver (Ag) → Silver sulfide (Ag₂S) → Blackening - Copper (Cu) → Copper sulfide (CuS, etc.) → Brown to black It gradually progresses through contact with sulfur compounds (H₂S, SO₂, etc.) in the air or surrounding materials. The causes include: - Sulfur gas in the air or polluted environments - Sulfur content in rubber, resin, adhesives, paper, and cardboard - Human sebum and high-temperature, high-humidity environments The impacts include: - Poor conductivity due to increased contact resistance - Decreased solderability - Appearance defects and reduced reliability Effective countermeasures include: - Sealed storage + use of desulfurizing agents and drying agents - Avoiding packaging materials that contain sulfur Sulfide formation can be prevented or delayed with proper management. [Nihon Denpaku Kogyo Co., Ltd.] 1-137 Nisshin-cho, Kita-ku, Saitama-shi, Saitama 331-0823 Tel: 048-665-8135 Fax: 048-665-8130

Plating Equipment