Operating Specification for Rust Prevention of Molds During Long-Term Shutdown and Storage
After finishing production batches, molds scheduled for prolonged idle storage face high risks of corrosion on cavities, guide pins, ejectors, slides and cooling channels. Moisture, decomposed plastic residues and release agent contaminants continuously corrode mold surfaces, creating pits and etching marks. Severe surface damage demands costly repairs and delays restart debugging. Implementing standardized rust prevention and sealing procedures protects mold precision and ensures smooth resumption of production after long storage periods.
1. Pre-Shutdown Cleaning Operations
Thorough removal of contaminants is required before formal storage. Residues trapped on mold surfaces accelerate electrochemical corrosion over time. Empty the barrel completely, eject all residual plastic inside molds, and clear carbon deposits, glue residues and release agent contaminants on cavities, cores and inserts. Soft copper scrapers and lint-free cloths matched with dedicated mold cleaner are recommended for wiping molding surfaces. Steel brushes and sandpaper cannot contact polished or textured areas to prevent surface scratches. Disassemble slides, angle lifters and ejector assemblies to clean plastic dust inside guiding gaps and clear vent channels, avoiding moisture accumulation in enclosed spaces. Circulate high-pressure clean water through cooling channels to flush scale and impurities, then blow all pipelines thoroughly with dry compressed air to eliminate trapped water, the primary cause of water channel rust. Remove oil stains and metal debris on mold base exteriors, and eliminate all water leakage risks before rust protection treatment.
2. Zoned Rust Preventative Spraying and Protection Treatment
Select appropriate anti-rust materials according to functional mold zones. Hard-film long-term rust inhibitor is preferred for extended idle periods. Apply uniform coating of hard-film rust preventive onto cavities, cores, textured and polished surfaces. Maintain moderate film thickness; excessive liquid trapped in dead corners creates cleaning difficulties during restart. Use narrow-nozzle spray nozzles to treat deep holes and insert clearances, ensuring no bare metal exposure. Apply combined lubrication and anti-rust grease to guide pins, guide bushes, ejectors, angle lifters and slides to maintain smooth sliding after storage. Drip small amounts of rust inhibitor into threaded holes and locating pin holes, then install dust plugs for sealing. Seal both ends of cooling channels with waterproof plugs to block ambient moisture. Avoid heavy exposure of sealing rings and hot runner gaskets to anti-rust oil, as prolonged oil immersion accelerates rubber aging. After spraying, close the mold under low clamping force with a tiny gap reserved; do not fully lock under high pressure to prevent squeezing and drying of protective oil film.
3. External Mold Encapsulation and Warehouse Environment Control
Complete overall sealing after anti-rust treatment to isolate humid air and dust. Protect lifting points, then wrap the entire mold with multi-layer moisture-proof plastic film. Place desiccant bags underneath molds. For large molds, insert extra desiccants into parting line gaps and schedule periodic replacement. Safeguard mold nameplates, datum corners and machining reference surfaces against lifting collision. Store molds in temperature-controlled dry warehouses with relative humidity below 60%. Keep molds away from windows and water pipelines prone to dampness. Place molds on dedicated wooden pallets instead of direct ground contact to prevent ground moisture erosion. Establish mold storage files recording sealing date, rust inhibitor model and scheduled restart date for regular inspection. Perform visual inspection every two months for molds sealed over three months, checking film integrity, condensation and oil film degradation. Reapply anti-rust treatment if protection fails.
4. Mold Unsealing and Restart Precautions
Improper unsealing may induce secondary damage. After removing outer wrapping, take out desiccants and slowly separate mold halves. Use lint-free cloth and dedicated mold cleaner to fully remove rust inhibitor film on cavities and all moving components. Remove channel plugs and circulate cooling water to verify unobstructed pipelines free of rust debris. Wipe guide pins, ejectors and slides clean, then reapply mold lubricant. Manually cycle mold opening, closing and ejection repeatedly to confirm smooth operation without jamming or abnormal noise. Dry cavities after cleaning and inspect molding surfaces for rust and spots before machine installation and trial molding. Treat minor rust spots gently with professional mold polishing compounds. Molds with deep corrosion pits require maintenance before production to avoid appearance defects on molded products.
Conclusion
Long-term mold rust prevention is systematic management. Thorough pre-storage cleaning lays the foundation. Targeted application of anti-rust media determines protection effectiveness. Sealing and warehouse control slow oil film deterioration. Standardized unsealing prevents secondary surface damage. All steps are interlinked. Simply spraying rust inhibitor without removing residues, drying cooling channels or implementing moisture encapsulation still leaves corrosion risks. Strict execution of this specification avoids mold corrosion damage during prolonged shutdowns, reduces maintenance workload before restart, stabilizes molding precision and extends overall mold service life.
