Causes: High temperatures and humidity in summer; water stains, mold release agent residues, chloride ions, and fingerprints. High-copper alloys (e.g., ADC12) are particularly prone to white spots, pitting, and blackening.

Prevention

1. Cleaning: Remove mold release agent and oil; use purified water for the final rinse and strictly control chloride ion levels; blow out accumulated water from blind holes and crevices.

2. Drying: Dry with hot air at 50–60°C; ensure parts are completely dry with no water stains remaining.

3. Protection: Prioritize chromium-free passivation; use anti-rust oil for short-term protection between processes.

4. Packaging: Use VCI (Volatile Corrosion Inhibitor) bags and desiccant; seal securely; elevate pallets—do not place directly against floors or walls.

5. Storage: Maintain warehouse humidity at ≤50% RH (use dehumidifiers); wear gloves—bare-hand contact is prohibited; implement FIFO (First-In, First-Out) to minimize inventory duration.

Treatment for Oxidized Parts

1. Mild white spots: Clean/remove oxidation → Rinse with purified water → Thoroughly dry → Re-passivate/apply anti-rust treatment.

2. Severe corrosion pitting: Sandblast or grind to remove the corroded layer; assess dimensions before further surface treatment; scrap parts with severe damage.

Key Control Points

Failure to dry completely = guaranteed oxidation; do not store unprotected parts in humid environments.