Complete Zinc-nickel Alloy Electroplating Process Specification For Grade 8.8 Screws Of New Energy Battery Packs, Based On GB/T10125 Zinc-nickel Plating National Standard

Complete Zinc-nickel Alloy Electroplating Process Specification For Grade 8.8 Screws Of New Energy Battery Packs, Based On GB/T10125 Zinc-nickel Plating National Standard

Power battery packs suffer trace electrolyte corrosion and high-low temperature cycle working conditions all year round. Ordinary electro-galvanizing only reaches 240 hours salt spray resistance, failing to meet the 1000-hour durability requirement of vehicle OEMs. Zinc-nickel alloy coating becomes the standard process for vehicle-grade battery screws due to superior anti-corrosion performance. Grade 8.8 high-strength carbon steel screws easily absorb hydrogen during electroplating, leading to unpredictable hydrogen embrittlement fracture after storage. This article fully standardizes full-process parameters including hydrogen removal, coating ratio and passivation sealing, covering standardized control from incoming degreasing to finished hydrogen embrittlement inspection.

1. Core Process Parameter Comparison Table For Two Zinc-nickel Coatings With Different Nickel Content

2. Mandatory Control Procedures For Full Zinc-nickel Plating Flow

1. Multi-stage Degreasing & Oil Removal: Hot alkaline degreasing + ultrasonic water washing to eliminate rolling oil residue causing coating peeling; 2. Weak Acid Activation Micro-etching: Short-time activation with 5% dilute hydrochloric acid, over-pickling leading to substrate intergranular corrosion is forbidden; 3. Pre-plating Base Layer Process: Thin zinc pre-plating improves substrate adhesion and reduces main coating stress; 4. Main Tank Zinc-nickel Alloy Plating: Real-time monitor nickel ion concentration, test tank liquid ratio every 4 hours; 5. 230℃ Constant Temp Hydrogen Removal Baking: Put into furnace within 4 hours after plating, hold temperature for 3 hours to eliminate hydrogen penetration risk; 6. Chrome-free Sealing Passivation: Adapt to battery environmental requirements, avoid hexavalent chromium residue polluting electrolyte.

3. Three Mass Production Defect Causes & Rectification Plans

1. Large-area coating peeling & falling off: Unclean workpiece oil stain, missing pre-plating process; Rectify: Extend ultrasonic degreasing time, add pre-plating station, replace degreasing liquid regularly. 2. Fracture after 1~2 weeks storage (hydrogen embrittlement): No high-temperature hydrogen removal execution, excessive hydrogen concentration in plating tank; Rectify: Strictly implement 230℃/3h hydrogen removal, add hydrogen suppression additive to tank liquid, shorten strong acid activation time. 3. Early red rust in NSS test: Insufficient coating thickness, failed passivation sealing; Rectify: Extend plating time to raise film thickness, replace long-acting chrome-free sealing agent, control passivation PH range 4.0~4.5.

4. Mandatory Coating Acceptance Standard For Battery Screws Of Vehicle OEMs

1. 15% high-nickel zinc-nickel coating with minimum 10μm film thickness is mandatory for areas contacting sealed electrolyte; 2. All zinc-nickel plated parts must attach third-party hydrogen embrittlement delayed fracture test report; 3. Chrome-containing passivation process is forbidden, no oil stain, white spot or missing coating after sealing; 4. Randomly extract 10 pieces per batch for 1000-hour NSS test, goods can only be delivered after passing without red rust.